California Democrats performed some addition by subtraction this week when congressional candidate Michael Kotick ended his bid to unseat Republican Rep. Dana Rohrabacher, and endorsed a fellow Democrat. Kotick, a former Nestle executive, said he decided to drop out in the name of party unity, the second Democratic candidate in Rohrabacher’s district to call it quits in the past few weeks.

Kotick was one of seven Democrats vying for the nomination, and, in any other state, his withdrawal would count as only minor news. But in California, where nonpartisan primaries mean the top two candidates advance to the general election, Democrats are worried that having too many good candidates might lead to losses in some winnable districts.

California Democrats hope other congressional hopefuls follow suit, both in Rohrabacher’s district and in more than a half-dozen others where Democrats are hoping to flip seats from red to blue. If they don’t, the quirks of the state’s unique primary system could leave Democrats without a candidate on the ballot come November. As Eric Bauman, chair of the California Democratic Party, put it at his state party convention earlier this year: “We have an overpopulation problem.”

The so-called jungle primary system, in which all the candidates appear on the same ballot, with the top two vote-getters advancing to the general election, 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 have found some recent success in culling the herd, but not nearly enough to ensure its survival.

Nowhere is that more evident than in California’s 48th Congressional District, where Rohrabacher is running for his 16th term. The Democratic Congressional Campaign Committee has his seat on its ambitious wish list, and non-partisan handicappers see the race as a toss-up. But that won’t matter if the six Democrats still running to unseat the incumbent split the vote in such a way where none of them survive the June 5 primary.

Democrats can’t seem to rally behind a single challenger there. Kotich and Laura Oatman, who dropped out last month, are both backing businessman Harley Rouda, but the state Democratic Party voted in February to endorse Rouda’s rival, stem-cell researcher Hans Keirstead. Making matters worse for Democrats was the late entry last month 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 five Republicans hoping to set up an all-GOP showdown with Rohrabacher in November.

It’s not just Rohrabacher’s district where Democrats are facing this nightmare scenario. The DCCC is also targeting nine other California seats that are currently held by Republicans, including three where Democrats appear to have even-odds of upsetting an incumbent and another two where they have better-than-even odds of claiming a seat of a GOP congressman who is retiring. But in more than half of those districts, there are at least four Democrats running, setting up the same risk of intra-party cannibalization on primary day. (Republicans face similar problems with so many candidates of their own in many of those races, but they are far less likely to get shut out, given the advantages of incumbency and the conservative tilt of those districts.) According to analysts at the political research firm California Target Book, there’s a very real possibility Democrats could get shut out in six of those races, including Rohrabacher’s. That could prove particularly costly to Democrats’ hopes of winning control of the House, given partisan gerrymandering and geographical quirks have already made that task more difficult than it should be.

There are no easy answers for Democrats. Standing by doesn’t seem like much of an option, but it isn’t clear Washington Democrats have either a carrot or a stick to thin the field. The DCCC hasn’t ruled out getting involved directly, but they risk muddling the race further if they are seen as putting their thumb on the scale from Washington. Meanwhile, as is the case nationwide, many of the Democrats running in California are first-time candidates with little connection to the establishment, making it more difficult to entice them to bow out for the good of the party. In the big picture, having too many credible candidates is a good problem to have, of course. But in a state with 53 congressional seats, it’s still a pretty big problem.