MANNING, N.D. -- Shirley Meyer grew up on a ranch north of Dickinson, N.D., and has represented her rural district in the state House for a decade. But when she knocks on doors in her re-election campaign, she sometimes feels like a stranger in her own home.

"I was just shocked at how many new people there were," Meyer said during a recent campaign swing through a south Dickinson mobile home park. "I didn't see one North Dakota (license) plate."

The oil boom that has transformed North Dakota's economy and reshaped the rolling prairie landscape has also added an element of mystery to next week's election by adding thousands of potential new voters to the region's tiny electorate. And the political suspense is tied to the national question of which party controls the Senate in January.

North Dakota's contest is one of several states with Senate contests that have remained tied for months, with no signs of clarifying before Tuesday's election. A handful of them, such as Montana's Senate race one state west, may not even be resolved then.

Republicans are still looking to gain four seats they need to win the Senate majority if President Barack Obama wins reelection, three if GOP presidential hopeful Mitt Romney prevails.

Workers from all over the country have pouring into western North Dakota for jobs in the booming Bakken oil shale region. Dickinson, a city of 16,000 that didn't grow at all between 1990 and 2000, is now surging past 20,000 residents, with acres of new temporary housing. By one state measure, the number of oilfield workers has increased from 5,600 to 14,000 since the last presidential election. And many of the new arrivals are eligible to vote.

What that means for North Dakota politics, or individual candidates, is anyone's guess.

"I'm just hoping that I have enough ballots," said Joan Hollekim, the county auditor in Mountrail County, North Dakota's biggest oil producer. She increased her ballot printing order by 25 percent, and already has more than 600 early votes, a record.

Beth Innis, the auditor in neighboring Williams County, said she's already booked more than 2,500 absentee votes, which is double what she expected.

"I thought it would be big," Innis said of the rising number of voters. "I didn't think it would be this big."

In North Dakota, the only state that does not have voter registration, any citizen over 18 who has lived in the same place for at least 30 days can cast a ballot. That would include oilfield workers who may actually be living elsewhere and commute home to see their families.

Democrat Heidi Heitkamp and Republican Rick Berg are both pitching hard for the votes of North Dakota's energy workers. In a final campaign swing this week, Berg visited an oilfield trucking service company, a natural gas processing plant and a coal mine in western North Dakota.

Heitkamp talks up her advocacy for North Dakota's oil and coal industries when she served as state attorney general and tax commissioner. In one of her television ads, she speaks over the noise of a passing train of oil tanker cars while promising to support development of a new North Dakota refinery to process crude.

The oil industry is making sure its work force knows how to participate. A recent newsletter from the North Dakota Petroleum Council instructed workers who live in recreational vehicles or "skid shacks"_ tiny huts, often no larger than a single-car garage, which can be hauled on flatbed trailers – how to request mail ballots.

The Brighter Future Alliance, a nonprofit group with ties to prominent North Dakota Republicans, has conducted voter information workshops in several of the temporary housing camps dotted throughout western North Dakota.

"We have focused on what we think is a critical thing for the country, and that is to pursue domestic energy supplies..." said Shane Goettle, an alliance official and former aide to Republican Sen. John Hoeven. "I think they can well be motivated to show up."

It's unclear how many new workers will vote.

Patty Caldwell, who started cleaning trailer houses at North Dakota oil well drilling sites more than a year ago to stave off foreclosure of her home in Oregon, said she wanted to make her voice heard.

"I just figured that I'm part of this community now," said Caldwell, whose company is in New Hradec, a hamlet about 10 miles north of Dickinson. "I have friends here. There's issues that I'm concerned about."

Monty Leonard, who drives a truck for a company that hauls water for the oil industry, came here from Oklahoma two years ago. He is casting his first vote in North Dakota.

Leonard said he has been following the presidential campaign, but is not familiar with the North Dakota candidates.

"I haven't been here very long, so I don't know the people," Leonard said of the candidates.

The potential magnitude of the oilfield vote – if it votes – is clearly visible. Across the area, rows of temporary trailers are plunked in the middle of brown, treeless pastures, while smoke-belching earth movers prepare space for new housing developments and business construction.

This year, as many as 4,300 new voters have been added to a state voter database in the nine largest oil-producing counties. That's more people than live in 26 of North Dakota's 53 counties, and a significant number in a state where 160,000 votes could elect either Berg or Heitkamp in their closely fought race.

Almost 533,000 North Dakotans are eligible to vote, a 7 percent increase since the last presidential election, the state Commerce Department says.

Meyer, a Democrat, said she has tried to "hit the new areas" in her re-election campaign.

She said some of the workers had absentee ballot paperwork.

"The vast majority of them that I visited with said, `We work 16 hours a day, and we have no intention of voting" in North Dakota, she said.

Other lawmakers said they doubted the new residents would be rushing to the polls.

"I don't think they're going to influence (election results) a lot for the local stuff. They're really just doing their work, and sending money home to their families," said state Rep. Bob Skarphol, a Republican from Tioga.

Related on HuffPost:

Loading Slideshow...
  • Robert Byrd (D-W.V.)

    <strong>Dates of service:</strong> Jan. 3, 1959 to June 28, 2010 <strong>Years of service:</strong> 51 years, 5 months, 26 days <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Sen. Robert Byrd, D-W.V., appears at a Senate hearing on May 9, 2007 in Washington. He died on June 28, 2010 at the age of 92. (KAREN BLEIER/AFP/Getty Images)

  • Daniel Inouye (D-Hawaii)

    <strong>Dates of service:</strong> Jan. 3, 1963 to Dec. 17, 2012 <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Senate Appropriations Defense Subcommittee Chairman Daniel Inouye (D-HI) speaks at a May 18, 2011 hearing in Washington. (Chip Somodevilla/Getty Images)

  • Strom Thurmond (R-S.C.)

    <strong>Dates of service:</strong> Dec. 14, 1954 to April 4, 1956 and Nov 7, 1956 to Jan 3, 2003 <strong>Years of service:</strong> 47 years, 5 months, 8 days <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Senator Strom Thurmond, R-S.C., pictured on May 22, 1997. He died on June 26, 2003 at the age of 100. (STEPHEN JAFFE/AFP/Getty Images)

  • Edward Kennedy (D-Mass.)

    <strong>Dates of service:</strong> Nov. 7, 1962 to Aug. 25, 2009 <strong>Years of service:</strong> 46 years, 9 months, 19 days <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Sen. Edward Kennedy (D-Mass.) speaks during a Jan. 21, 2007 taping of NBC's "Meet the Press." He died on Aug. 25, 2009 at the age of 77. (Photo by Alex Wong/Getty Images)

  • Carl Hayden (D-Ariz.)

    <strong>Dates of service:</strong> March 4, 1927 to Jan. 3, 1969 <strong>Years of service:</strong> 41 years, 9 months, 30 days <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> President Lyndon Johnson presents a pen to Sen. Carl Hayden, D-Ariz., on September 30, 1968 in Washington. Hayden died on Jan. 25, 1972 at the age of 94. (AP Photo)

  • John Stennis (D-Miss.)

    <strong>Dates of service:</strong> Nov. 5, 1947 to Jan. 2, 1989 <strong>Years of service:</strong> 41 years, 1 month, 29 days <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> John Stennis, chairman of the Senate Armed Services Committee, speaks on the July 6, 1969 edition of ABC's "Issues and Answers." Stennis died on April 23, 1995 at the age of 93. (AP Photo)

  • Ted Stevens (R-Alaska)

    <strong>Dates of service:</strong> Dec. 24, 1968 to Jan. 2, 2009 <strong>Years of service:</strong> 40 years, 10 days <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> In this Tuesday, April 7, 2009 file photo, former Sen. Ted Stevens arrives at federal court in Washington. Stevens died in a plane crash on Monday, Aug. 9, 2010 at the age of 86. (AP Photo/Gerald Herbert, file)

  • Patrick Leahy (D-Vt.)

    <strong>Dates of service:</strong> Jan. 3, 1975 to present <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Sen. Patrick Leahy, D-Vt., stands in front of the U.S. Capitol building on Monday, Nov. 26, 2007. (AP Photo/Charles Dharapak)

  • Ernest Hollings (D-S.C.)

    <strong>Dates of service:</strong> Nov. 9, 1966 to Jan. 2, 2005 <strong>Years of service:</strong> 38 years, 1 month, 25 days <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Sen. Ernest Hollings, D-S.C., appears at a Town Hall on Thursday, Oct. 7, 1983. He ran for the 1984 Democratic presidential nomination, but lost out to Vice President Walter Mondale. (AP Photo/Ron Frehm)

  • Richard Russell (D-Ga.)

    <strong>Dates of service:</strong> Jan. 12, 1933 to Jan. 21, 1971 <strong>Years of service:</strong> 38 years, 19 days <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Sen. Richard Russell (D-Ga.), shown from his Senate office desk in Washington on July 14, 1942. Russell died on Jan. 21, 1971 at age 73. (AP Photo/Eugene Abbott)

  • Russell Long (D-La.)

    <strong>Dates of service:</strong> Dec. 31, 1948 to Jan. 2, 1987 <strong>Years of service:</strong> 38 years, 3 days <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Russell Long, shown at his desk in Baton Rouge, La., on Feb. 21, 1948. Long died on May 9, 2003 at age 84. (AP Photo)

  • Orrin Hatch (R-Utah)

    <strong>Dates of service:</strong> Jan 3. 1977 to present <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> U.S. Sen. Orrin Hatch (R-Utah) heads to a weekly policy meeting at the Capitol on March 20, 2012 in Washington. (Photo by T.J. Kirkpatrick/Getty Images)

  • Francis Warren (R-Wyo.)

    <strong>Dates of service:</strong> Nov. 18, 1890 to March 3, 1893 and March 4, 1895 to Nov. 24, 1929 <strong>Years of service:</strong> 37 years, 4 days <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> (Photo by Alex Wong/Getty Images)

  • James Eastland (D-Miss.)

    <strong>Dates of service:</strong> June 30, 1941 to Sept. 28, 1941 and Jan. 3, 1943 to Dec. 27, 1978 <strong>Years of service:</strong> 36 years, 2 months, 24 days <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Sen. James O. Eastland of Mississippi, is shown in Washington on March 25, 1971. Eastland died on Feb. 19, 1986 at age 81. (AP Photo / Charles Tasnadi)

  • Warren Magnuson (D-Wash.)

    <strong>Dates of service:</strong> Dec. 14, 1944 to Jan. 2, 1981 <strong>Years of service:</strong> 36 years, 20 days <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Then-Rep. Warren Magnuson (D-Wash.) smiles in his Washington office on Oct. 19, 1943. Magnuson died on May 20, 1989 at the age of 84. (AP Photo)

  • Joe Biden (D-Del.)

    <strong>Dates of service:</strong> Jan. 3, 1973 to Jan. 15, 2009 <strong>Years of service:</strong> 36 years, 13 days <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Democratic vice presidential candidate and U.S. Senator Joe Biden (D-Del.) speaks at a rally in support of then-Democratic presidential nomineee U.S. Sen. Barack Obama (D-IL) on October 12, 2008 in Scranton, Pa. (Photo by Jeff Fusco/Getty Images)

  • Pete Domenici (R-N.M.)

    <strong>Dates of service:</strong> Jan. 3, 1973 to Jan. 2, 2009 <strong>Years of service:</strong> 36 years <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> U.S. Republican Sen. Pete Domenici (R-N.M.) listens during the announcement of the America Competes Act on March 5, 2007 in Washington. (MANDEL NGAN/AFP/Getty Images)

  • Richard Lugar (R-Ind.)

    <strong>Dates of service:</strong> Jan 3. 1977 to Jan. 3, 2013 <strong>Years of service:</strong> 36 years <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Sen. Richard Lugar attends a courtesy call to the Malacanang Palace in Manila on October 29, 2012. (NOEL CELIS/AFP/Getty Images)

  • Claiborne Pell (D-R.I.)

    <strong>Dates of service:</strong> Jan. 3, 1961 to Jan. 2, 1997 <strong>Years of service:</strong> 36 years <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> U.S. Sen. Claiborne Pell, D-R.I., announces on Sept. 5, 1995 that he would not seek a seventh term in office. Pell died on Jan. 1, 2009 at age 90. (AP Photo/Charles Krupa) (AP Photo/Charles Krupa, File)

  • Kenneth McKellar (D-Tenn.)

    <strong>Dates of service:</strong> March 4, 1917 to Jan. 2, 1953 <strong>Years of service:</strong> 35 years, 10 months <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Sen. Kenneth McKellar (D-Tenn) left, and James M. Landis, OCD director meet on Feb. 27, 1942. McKellar died on Oct. 25, 1957 at age 88. (AP Photo)

  • Milton Young (R-N.D.)

    <strong>Dates of service:</strong> March 12, 1945 to Jan. 2, 1981 <strong>Years of service:</strong> 35 years, 9 months, 22 days <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Secretary of State Henry Kissinger, left, chats to Senator John L. McClellan (D-Ark.), center, and Senator Milton Young (R-N.D.), at the White House in Washington, March 24, 1975. Young died on May 31, 1983 at the age of 85. (AP Photo)

  • Ellison Smith (D-S.C.)

    <strong>Dates of service:</strong> March 4, 1909 to Nov. 17, 1944 <strong>Years of service:</strong> 35 years, 8 months, 13 days <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Sen. Ellison Smith (left) meets with Secretary of Agriculture, Henry Wallace (right) on Jan. 18, 1934 in Washington. Smith died on Nov. 17, 1944 at age 80. (AP Photo)

  • Allen Ellender (D-La.)

    <strong>Dates of service:</strong> Jan. 3, 1937 to July 27, 1972 <strong>Years of service:</strong> 35 years, 6 months, 24 days <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Sen. Allen Ellender, D-La., bids goodbye to Mrs. Ladybird Johnson after a gumbo luncheon at the Capitol on August 21, 1964. Ellender died on July 27, 1972 at age 81. (AP Photo)

  • William Boyd Allison (R-Iowa)

    <strong>Dates of service:</strong> March 4, 1873 to Aug. 4, 1908 <strong>Years of service:</strong> 35 years, 5 months <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a>

  • Thad Cochran (R-Miss.)

    <strong>Dates of service:</strong> Dec. 27, 1978 to present <strong>Source:</strong> <a href="http://www.senate.gov/senators/Biographical/longest_serving.htm">United States Senate</a> Republican US Senator from Mississippi Thad Cochran attends a joint press conference with US Ambassador to Iraq Zalmay Khalilzad and Iraqi Planning Minister Barhem Saleh (not seen), in Baghdad's Heavily fortified Green Zone, 19 April 2006. (SABAH ARAR/AFP/Getty Images)