Former Rep. Quico Canseco (R-Texas) has been forced into a runoff in his primary, a result that could boost Rep. Pete GallegoPete P. GallegoObamaCare repeal vote: 15 GOP lawmakers to watch Vulnerable Texas GOP lawmaker survives rematch 5 races for tech to watch MORE's (D-Texas) reelection chances.

Canseco leads former CIA agent Will Hurd by 41 percent to 40 percent, below the 50 percent needed to win the primary outright. The two will now face off in a runoff election in late May, which will further sap their already-depleted campaign accounts.

The freshman Gallego holds the only swing district in Texas, a heavily Hispanic one rooted in San Antonio. Mitt Romney won it by three percentage points in 2012, while Gallego defeated Canseco by 5 percentage points.

Republicans have been hopeful about their chances against Gallego in an off-year election where Hispanic turnout drops, making him more vulnerable.

But Hurd and Canseco will struggle to catch up in fundraising. Both had less than $200,000 left in the bank as of mid-February and will have to keep spending ahead of the runoff race. Gallego had more than a half-million dollars in the bank as of last month.

Some Republican strategists also believe they need a Hispanic candidate to compete in the district, making the former one-term lawmaker's showing more disappointing.