House Democrats on Friday waded into a crowded congressional primary in California, backing businessman Harley Rouda in a high-profile race for the seat currently held by Republican Rep. Dana Rohrabacher. The move to back Rouda, over stem-cell researcher Hans Keirstead, comes as Democrats face the prospect of being left off the November ballot in a district they could conceivably win. It’s a problem for the party in a half-dozen key congressional races across California, thanks to the state’s novel system of so-called “jungle primaries,” in which both parties compete in a single primary and the top two finishers advance to the general election.

Democrats have been struggling to winnow the field of candidates in those districts, in the hopes of consolidating their votes and making sure at least one of their candidates makes the general-election ballot. In Rouda’s case, the Democratic Congressional Campaign Committee added Rouda to its Red to Blue program, designed to elevate those candidates the party believes are best suited to flip key House seats. While not an official endorsement, it’s about as close as the DCCC gets in a primary. It’s also a bit of a surprise that the group went with Rouda over Keristead given the latter won the endorsement of the state party earlier this year and previously said he was aggressively recruited to get into the race by the same DCCC that is now backing his rival. But there were recent signs the party was moving toward Rouda, and the Los Angeles Times reports that the final decision came down partly to internal polling suggesting he is better positioned to snag one of the two nominations next month.

The jungle primary system can be a boon to Democrats in statewide elections—see the all-Democratic Senate race in 2016 or the soon-to-be all-Democratic Senate contest in 2018—but this year it’s threatening to spoil the party’s chances to reclaim the majority in the House.

Democrats face the possibility of being locked out of as many as six key races in the state, but they are most worried about three, all of which are seen as flippable after Hillary Clinton won those districts two years ago: the 39th, where Republican GOP Rep. Ed Royce is retiring; the 49th, where Republican Rep. Darrel Issa is retiring; and the 48th, where Rohrabacher is seen as vulnerable.

The problem for Democrats is that they can’t flip those GOP seats if they don’t have someone on the ballot in November. As an incumbent, Rohrabacher appears to be a lock for a top-two finish in the June primary, leaving five Democrats and four Republicans battling it out for the second spot. Democrats had some success culling the field when a pair of candidates recently dropped out and endorsed Rouda. But complicating matters was the relatively late entry of Scott Baugh, a former county GOP chairman and state assemblyman. With his deep political ties in the district, Baugh entered the race as the clear leader among the pack of Republicans hoping to set up an all-GOP showdown with Rohrabacher in November, and recent polling from the state suggests he, Rouda, and Keristead are all in a battle for second.

The DCCC’s decision to get involved marks the second time in as many months that the group has picked sides in a contested primary in California. The group previously tapped lottery winner-turned-philanthropist Gil Cisneros over five other Democrats hoping to replace Royce, a decision that ruffled a few feathers in the district. The DCCC has also gotten involved in Issa’s district, albeit a little more creatively. Instead of backing one of the four Democrats fighting amongst themselves there, the DCCC started airing attack ads against two second-tier GOP candidates in that race—instead of the Republican out in front in the polls—in hopes of making room for a Democrat in the general election.

The DCCC’s decision to back Rouda is sure to anger some swath of the left, as the group has to varying degrees in other parts of the country whenever it has played favorites. But the group also has good reason to think that anger will be forgiven, if not forgotten, before long.