A federal judge has rejected a lawsuit from two Bernie Sanders supporters over voting rules in next week’s California primary. The suit sought to make it easier for California independent voters to cast ballots in the presidential race.

California voters registered as “no party preference” are allowed to cast ballots in the Democratic presidential primary – but they don’t automatically receive presidential ballots. They have to ask for them. That’s easy enough when voting in person, but independents who vote by mail must request Democratic ballots from their county’s elections office.

That’s what drew the lawsuit from the Sanders supporters. They argued those rules were too confusing – and elections officials weren’t doing enough to educate voters, increasing the risk of disenfranchisement. They asked the state to extend the registration deadline and allow write-in votes.

But a San Francisco judge said no, which leaves the Sanders campaign with a lot of work to do. In previous primary contests and in California polls, the Vermont senator has drawn some of his strongest support from independents. But according to the Sacramento firm Political Data, Incorporated, just 15 percent of eligible “no party preference” Californians who vote by mail have requested Democratic primary ballots.