https://www.nytimes.com/2018/04/21/us/politics/democrats-house-midterms-california.html

«They are moving most aggressively in California, where the state’s nonpartisan primaries present a unique hazard: State law requires all candidates to compete in the same preliminary election, with the top two finishers advancing to November. In a crowded field, if Democrats spread their votes across too many candidates, two Republicans could come out on top and advance together to the general election.»