A controversial Republican gubernatorial candidate in California could cause the GOP headaches in down-ballot House races in a state crucial to the party’s hopes of increasing its House majority.  

State Assemblyman Tim Donnelly led Neel Kashkari, a former U.S. Treasury official and the establishment-preferred candidate, by 5 points in a poll this month from the Public Policy Institute of California. That has top Republican operatives in California and Washington, D.C., concerned that Donnelly’s controversial comments and ties to the California Minutemen , a group that fights illegal immigration on the border, could mobilize Hispanic and other Democratic-base voters who otherwise might fall off in this midterm year.  

Their fear is that the increased turnout to oppose Donnelly could boost the re-election hopes of vulnerable House Democrats and perhaps even improve the party’s chances to add to its ranks in the already Democrat-heavy delegation. A consultant with ties to Kashkari is among the Republicans sounding the alarm. “It would be a fucking disaster,” said Jason Roe, a San Diego-based consultant who has worked with numerous congressional campaigns and whose firm is consulting for Kashkari.  

Democratic Gov. Jerry Brown is expected to finish way ahead of both Republicans in the June 3 top-two primary and is favored to win re-election in November. House Majority Whip Kevin McCarthy of California, who has led the party’s efforts at the congressional level in the state, noted in a brief interview Thursday that the GOP always has difficulty running statewide, so Republican House candidates must work to individualize their races.  

“Neither of them are polling really well,” McCarthy said. “I always think people run in their own districts. Statewide it’s tough.”  

Still, the party’s concern has been voiced over national airwaves. Karl Rove, founder of the GOP-aligned super PAC American Crossroads, which is spending on congressional races, said on the Hugh Hewitt radio show this month that the “outrageous things” Donnelly has said and done “will be used to tarnish” the state party and Republican candidates.  

While the gubernatorial race is an issue for the GOP, Republicans are expected to get three top-tier House candidates through primaries in competitive districts represented by freshman Democrats.  

Former Rep. Doug Ose is favored to take on Rep. Ami Bera in the 7th District; former Capitol Hill aide Brian Nestande is expected to face Rep. Raul Ruiz in the 36th District; and former San Diego City Councilman Carl DeMaio will take on Rep. Scott Peters in the 52nd District.  

They represent some of the party’s best pickup opportunities in the country, though President Barack Obama won all three in 2012. Crucial to Republicans winning back these seats is Democratic drop-off and a motivated GOP base. Republicans say Donnelly could keep moderate Republicans home, and motivate Democrats to head to the polls — effectively vanquishing a GOP advantage in the fall.  

“There were some seats that Republicans narrowly lost in 2012,” California Republican strategist Kurt Bardella said. “And Donnelly could have a harmful effect if he’s on the top of the ticket.”  

Similarly, Democrats have a prime pickup opportunity in the 21st District, where freshman GOP Rep. David Valadao is likely to face former Capitol Hill aide Amanda Renteria in a district Obama carried by 11 points in 2012. Higher Hispanic turnout in that district could be a boon for Renteria, whom Democrats tout as one of their top recruits this cycle.  

While Donnelly leads in polling of the gubernatorial race, Kashkari has the infrastructural advantages. He pulled in high-profile endorsements in the final weeks of the contest from Mitt Romney, former Secretary of State Condoleezza Rice and Rep. Darrell Issa. Plus, the San Francisco Chronicle reported Thursday that Kashkari’s investment of personal funds gave him a significant financial edge over Donnelly, while a super PAC formed to help Kashkari get through the primary received a massive influx of cash this week.  

Democrats have their own problems in the state, stemming from the top-two primary — where the two highest vote recipients advance to the general regardless of party.  

In the 31st District, it could be déjà vu for Democrats in a district they should have won in 2012. Retiring Republican Rep. Gary G. Miller and another Republican advanced there in 2012, when four Democrats splintered the vote, taking a seat off the map even though Obama carried it with 57 percent. Democrats are working to avoid a similar scenario this year.  

Still, Democrats in the state are jubilant about the possibility of a Donnelly candidacy as June 3 draws near. After a four-seat gain in 2012, the party is looking to increase its majority in the delegation.  

“I think Donnelly’s victory would motivate true blue Democrats, while Kashkari’s victory has the potential to change the dialogue for who votes Republican,” Los Angeles Democratic Party Chairman Eric Bauman said.  

Kyle Trygstad contributed to this report