05/29/2012 07:03 pm ET Updated May 29, 2012

Silvestre Reyes, Longtime Democratic Congressman, At Risk In Texas 16 Democratic Primary

Rep. Silvestre Reyes (D-Texas) may soon join Sen. Richard Lugar (R-Ind.) and Reps. Jean Schmidt (R-Ohio) and Tim Holden (D-Pa.) on an expanding list of members who can't hold their seat through the primary.

Despite prominent endorsements from former President Bill Clinton and President Barack Obama, the long-serving Reyes is in an extremely tight primary battle against newcomer Beto O'Rourke in Tuesday's election, analysts from El Paso told their local ABC affiliate this weekend. Both members spent hundreds of thousands on the race.

The close race had Reyes and his office in a flurry of activity today. O'Rourke, who received the endorsement of the El Paso Times, kept his office "noticeably calmer," according to a local ABC affiliate.

Reyes has encouraged a final push from his staff. In their last efforts, staff members identified more than 30,000 supporters, according to communications director Jose Borjon.

"We have been phone banking, block-walking, [and] visiting polling sites. We had a volunteer cook-out last night." Borjon told The Huffington Post. "We are working the election day hard [and] we are confident we will win."

O'Rourke, on the other hand, felt less pressure to ramp up his efforts as the clocked ticked down.

"This has been run like a marathon," O'Rourke said to ABC-7 in El Paso. "We started nine months ago and we've worked hard each and every day, working seven days a week throughout this, so there's nothing a mad sprint can win at this point."

Incumbency usually affords a candidate increased name recognition and access to networks of supporters and donors; less than 5 percent of members have lost their primaries in the past few decades. But with voters on both sides of the aisle expressing dissatisfaction with incumbent politicians, long terms have hurt several prominent lawmakers this year, including Lugar, who served six terms in the Senate.

Those anti-Washington criticisms have followed Reyes, who has served in Congress since 1997, throughout his campaign this cycle. O'Rourke, who served on the El Paso City Council for six years, has charged in recent ads that Reyes lost touch with his constituents during his tenure in office. One ad alleges Reyes used his office to secure jobs for his children, highlighting their employment with a company that was awarded a $200 million federal contract without a competitive bidding process. Reyes doled out $600,000 to himself and his family for campaign and consulting purposes in the last two election cycles.

O'Rourke's ads were in response to a Reyes television ad that attacked his character and accused him of having a criminal record. Reyes' ad displays a mug shot of O'Rourke after a drunken driving arrest as well as a video of the El Paso representative rolling around on the floor of a bar. Though O'Rourke was arrested twice in El Paso in the 1990s, but both cases were either declined or dismissed.

The anti-incumbent super-PAC, the Campaign for Primary Accountability, has helped O'Rourke in the race. The group, funded in part by TD Ameritrade founder Joe Ricketts, has spent $195,000 on television, radio and direct mail attacking Reyes.

The race also made headlines in February, when Reyes ran an ad about O'Rourke's support for ending the federal prohibition against marijuana. When he was on city council, O'Rourke pushed for a resolution calling on the federal government to reexamine that prohibition. Reyes called him an advocate, while O'Rourke defended his position, saying murder counts across the border demanded a reevaluation of the War on Drugs.