National Democrats announced Friday that they would back businessman Harley Rouda in the crowded field to unseat GOP Congressman Dana Rohrabacher, hoping to avoid being locked out of a targeted race that could prove pivotal to the Democrats’ effort to retake the House.

The Democratic Congressional Campaign Committee on Friday added Rouda to its Red to Blue program, tantamount to an endorsement in the race for the 48th Congressional District, which extends from Laguna Beach to Seal Beach. It’s one of five GOP-held seats in Southern California that national Democrats have targeted to flip in their effort to retake control of the House of Representatives.

California’s jungle primary system allows only the top two vote-getters to advance out of the June primary to the November general election, regardless of party affiliation. With eight Democrats on the ballot in the Rohrabacher race, the DCCC hopes its support will rally party voters around a single challenger. That would make it less likely the vote splits in a way that leads to an all-GOP November runoff – a scenario that became more plausible when Republican Scott Baugh, the former chair of the county GOP, entered the race in March.

Backing Rouda also seems to signal a shift in the DCCC’s assessment of the contest.

Last year, it assisted Rouda’s top Democratic opponent, stem-cell biologist Hans Keirstead, in launching his campaign. But on Friday, DCCC Chairman Ben Ray Luján said the group had determined that Rouda was “the strongest Democrat in this race and best prepared for the general election,” citing polling from Rouda’s campaign stating that he was the best positioned to beat Rohrabacher.

The two top Democrats have split endorsement in recent months. Keirstead won the California Democratic Party’s endorsement at the group’s February convention and has earned the support of Fran Sdao, chairwoman of the Democratic Party of Orange County.

Meanwhile, Rouda has been endorsed by the local chapter of Indivisible, a grassroots anti-Trump resistance group, and by several local Democratic members of Congress, including Linda Sanchez, Lou Correa and Alan Lowenthal. Two 48th District candidates who withdrew from the race in recent months also back Rouda.

Only hours after the DCCC announced its support of Rouda, Keirstead released its own polling stating that he was the top Democrat in the race, though still behind both Rohrabacher and Baugh.

“It’s disappointing that D.C. insiders have decided to put their thumb on the scale for Harley Rouda,” said Keirstead’s campaign spokesman Kyle Quinn-Quesada.

Republicans have a 10 percentage point voter registration advantage in the 48th Congressional District, but it swung to Hillary Clinton by 1.7 percentage points in the 2016 general election.

National Democrats have become increasingly active in Orange County’s congressional races in recent weeks, all in the effort of averting a Democratic lockout.

On Monday, the DCCC released cable TV ads attacking former State Sen. Bob Huff and Orange County Supervisor Shawn Nelson, who are running to replace retiring GOP Congressman Ed Royce in the 39th District. The ads, which cost north of $300,000, could be an effort to unify Republican voters behind a single GOP candidate, former Assemblywoman Young Kim, so that two Republicans don’t make the November ballot.

Correction: A previous version of this article misstated the margin by which Hillary Clinton bested Donald Trump in the 48th Congressional District in the 2016 general election.