California Democrats persuaded voters to let them redraw the state’s congressional map so the party could potentially gain five seats in the U.S. House to counter GOP redistricting in Texas. Tuesday’s primary will be the first indication of whether that will pay off.

The state’s unusual primary system, in which the top two vote-getters advance to the general election regardless of party, means Democrats have a chance of effectively missing out on a pickup in the San Diego suburbs, where Republican Rep. Darrell Issa’s district was redrawn to give it a slight Democratic lean.