Both Pelosi and McCarthy have good reason to complain. In the top-two system, which is sometimes called a jungle primary, the two candidates who receive the most votes advance to the November general election, regardless of their party affiliation. And because of those rules, both Democrats and Republicans are at serious risk of being shut out of key races this fall after California voters winnow the field in Tuesday’s primary.

National Democrats, however, have much more to lose. Party leaders are scrambling to ensure that at least one of their candidates makes it onto the ballot in a handful of competitive House races in and around Orange County in Southern California. They fear that the top-two nominating system could turn one of the party’s 2018 strengths—a burst of anti-Trump grassroots enthusiasm—into a liability: In a trio of GOP-held districts that Hillary Clinton carried in 2016, several viable Democrats are running, raising the possibility of a splintered vote that could allow two Republicans to narrowly capture the general-election slots. With control of the House at stake in November, having only Republicans advance in these districts could jeopardize the Democrats’ chances to retake the majority.