Both Bernie Sanders and Hillary Clinton visited Los Angeles Monday to try to gin up new voters and campaign contributions. May 23 is the last day for voters to register to be eligible to vote in the June 7 California primary. That deadline to register could be pushed back, however, if a group of Bernie Sanders supporters has its way. They’ve filed a lawsuit demanding an extension to the deadline, saying that independent voters in California planning to mail in their ballots are being shut out of the Democratic primary because of confusing registration rules. In California’s 2012 primary, 65 percent of primary ballots cast were cast by mail. So why are the requirements so confusing?