Rep. Lloyd Doggett (D-Texas) was outraised by primary opponent and Texas state Rep. Joaquin Castro (D) by $500,000 to $375,000 in the last quarter, but has $3.3 million in the bank to try and fend off the challenge.

Doggett faces a potentially tough reelection battle this year because Texas Republicans fractured the Anglo Democrat's Austin-based district and stretched it to include heavily Hispanic parts of San Antonio. The district is now about half in San Antonio and 20 percent in Austin, and Hispanic-majority.

Castro, the twin of San Antonio Mayor Julián Castro, has a strong fundraising network in the city that he has begun to expand into Doggett's territory in Austin, with a fundraiser that included top Obama fundraiser Kirk Rudy and Container Store scion and major Democratic donor Aimee Boone.

But some of Castro's donors have also been major Republican benefactors, including AT&T executive and former state Sen. John Montford (D-Texas), who has crossed party lines to back Gov. Rick Perry, and NuStar Energy CEO Bill Greehey.

These supporters could be backing Castro just to eliminate Doggett, who has long been a thorn in Perry's side.

Castro's campaign manager had another idea, saying their support did not reflect on his policies or Perry supporters' hopes to retire Doggett but their frustration with Washington.

"Clearly those business guys in SA know the Castro brothers, his identical twin is the mayor of SA, and they know these guys are tried and true Democrats," said Castro campaign manager Christian Archer. "They're sick and tired of the partisan bickering and the do-nothing Congress. They're looking at Joaquin and say there's no doubt he's the most liberal member of the Texas statehouse but they know he can get things done and work across the aisle."

Doggett has proven that he has some crossover appeal to Hispanics, winning a tough primary after Republicans endangered him in 2004 by dragging his district down to the Mexico border (it has since been redrawn). But that year most of the top-level Hispanic candidates declined to run. This time he hasn't been as lucky, and could face the toughest election of his House career.