DERRY, N.H. -- Mitt Romney's biggest fear heading into Tuesday's New Hampshire primary is voter complacency, not Republican rivals Newt Gingrich or Rick Santorum in a contest seen as his for the taking.
"Don't get too confident with those poll numbers. I watch polls come and go. Things change very quickly. It's very fluid," Romney told a crowd of 1,000 people at Pinkerton Academy on Saturday. "I need you guys to make sure your friends get out and vote, and you vote as well."
Romney's campaign has called this "Super Saturday" and embarked on an aggressive and organized push to make sure supporters actually vote. The concern is that New Hampshire's notoriously fickle primary voters could change their minds at the last moment or fail to show up at all.
"The only thing I'm worried about is working against the complacency that Mitt's up in the polls," said Jason McBride, who runs Romney's operation in this first-in-the-nation primary state. "That's the concern."
Romney has led the polls for so long and by so much in New Hampshire that victory is considered much more than conventional wisdom.
The former Massachusetts governor spent time this past week in South Carolina, which holds its primary Jan. 21. Much of Romney's staff from Iowa, where he eked out a victory Tuesday over former Pennsylvania Sen. Rick Santorum, is in place in South Carolina for the first contest in the South. There are plans for Romney's New Hampshire staff to head to Florida on Wednesday after the primary; the Florida contest is Jan. 31.
But campaign advisers worry that if they let up in New Hampshire now, Romney supporters are "going to watch the news and they're going to say, oh, `Mitt Romney's whooping' everybody, I don't need to vote,'" McBride said.
The poll numbers show Romney up by 20 percent or more over his closest rival, Rep. Ron Paul of Texas. Both lead Santorum and former House Speaker Newt Gingrich. It's an advantage that Romney has maintained for months.
But New Hampshire has never handed a primary victory to a Republican who also won Iowa, and voters often make up their minds late in the game.
Romney also needed to get debates Saturday night and Sunday morning that gave the other candidates a chance to throw the front-runner off stride.
"You never know. You never know what's going to happen," Romney's wife, Ann, told the crowd in Derry as she introduced one of her sons, Tagg, and several of her grandchildren.
That helps explain the campaign's finishing strategy to close the deal.
About 500 volunteers have arrived from states across the Northeast. They're working from the campaign's Manchester headquarters as well as from offices in Concord, Keene, Derry and Rochester that have opened in the past few weeks.
The goal was to call the 175,000 or so potential Romney supporters in the state. The campaign has paid for an additional 300,000 phone calls that started Thursday and will finish on Monday.
The 250 fresh volunteers from New Hampshire will try to knock on 10,000 doors before the weekend is over.
It's an effort unmatched by rivals who had focused on winning Iowa's caucuses before they could think about coming in to New Hampshire. Romney aides view Paul as the strongest possible rival; Santorum's national campaign manager, Mike Biundo, is a longtime New Hampshire operative.
Paul visited the Windmill Restaurant in Concord on Saturday, shaking hands and chatted with patrons. Paul had no other events until the evening debate. His son, Kentucky Sen. Rand Paul, planned to campaign on his behalf in Concord and Windham.
While Santorum spent time in New Hampshire earlier in the race, he had concentrated almost exclusively in Iowa through the winter.
Recognizing he was unlikely to topple Romney in New Hampshire, Santorum cast himself as a strong challenger to Obama for November.
"Who are you, who are you to say that every child in America should go to college?" Santorum said of the Democratic president during a forum at Saint Anselm College near Manchester. "If one of my kids wants to go and be an auto mechanic, good for him. ... It's the kind of snobbery from those who think they know how to run our lives."
Former Utah Gov. Jon Huntsman, who skipped the Iowa contest, said at a senior center in North Haverhill that voters who have been entertained by the ""circus acts" put on by other candidates are starting to turn serious.
Huntsman said they will choose him when they ask themselves which candidate has the best background, temperament and ability to bring the nation together.
As of last month, New Hampshire had about 232,000 registered Republicans, 223,000 Democrats and 313,000 undeclared voters, who can vote in either primary. The state also allows same-day voter registration at the polls.
New Hampshire Secretary of State Bill Gardner said he expects 250,000 ballots to be cast Tuesday. In 2008, when both parties had contested races, just over 241,000 ballots were cast in the GOP primary and 289,000 in the Democratic primary.
Associated Press writers Beth Fouhy in Concord, Philip Elliott in Goffstown and Holly Ramer in North Haverhill contributed to this report.