It's been a month since control of Congress was decided, but Republican Rep. Henry Bonilla and Democrat Ciro Rodriguez are still campaigning as if the balance hangs on the outcome of their runoff.

For incumbent Bonilla, a victory at the polls Tuesday would give him an eighth term representing Texas' largest congressional district, the 23rd.

For Rodriguez, it would mean a return trip to Washington after a two-year absence. He served in Congress during 1997-2005 but was ousted in the 2004 by Rep. Henry Cuellar.

Neither Bonilla nor Rodriguez received 50 percent of the vote in a crowded field Nov. 7.

Bonilla has been airing TV commercials criticizing Rodriguez for past votes, including one against establishing the Homeland Security Department. The Democratic Congressional Campaign Committee is airing ads for Rodriguez that attack Bonilla for what it says are cuts in veterans and military benefits.

Rodriguez resurrected reports that Bonilla employed an illegal immigrant British nanny for almost seven years, a small scandal that erupted in 1994. The Justice Department investigated but declined to charge anyone.

Rodriguez said he's relying on voters' dissatisfaction with Bonilla.

"They'll vote for you because they like you, but they'll also vote for you because they dislike the other guy," Rodriguez said. "You get them whichever way you can."

In a campaign this short, turnout from the base will be the key to a victory for either candidate, said Jason Casellas, assistant professor in government at the University of Texas at Austin.

"The people who are going to turn out in a special election are going to be the partisans," Casellas said.

A Rodriguez victory would be an additional blow to the Texas redistricting plan engineered by former House Majority Leader Tom DeLay in 2003, which allowed the GOP to pick up several congressional seats, said Gary Keith, a senior lecturer in government at UT Austin.

The DeLay plan moved 100,000 predominantly Democratic Laredo Hispanics out of the 23rd and into another district. However, the Supreme Court ruled in June that the new district unconstitutionally diluted Hispanic voting strength, and a new map was drawn in August by a three-judge panel.

Rodriguez lost to Cuellar in this year's District 28 primary. The redistricting put his San Antonio home in the redrawn District 23, allowing him to enter the race against Bonilla — with the endorsement of Cuellar.

The 23rd stretches along the Mexican border from San Antonio to the eastern edge of El Paso, yet immigration isn't listed on either of the Hispanic candidates' Web sites. Bonilla voted to build a border fence to fight illegal immigration; Rodriguez said he would not have.

"Because (immigration) is so divisive, which of the candidates could use the issue to really boost their turnout without really angering the opposition and boosting their turnout?" Keith said. "It may be an issue that's too radioactive. ... Because it could blow up on you as much as it could help you."