On August 21, California Republican congressman Duncan Hunter was indicted for campaign finance law violations. Because he placed first in the June 5 top-two primary, his name is on the November ballot, opposite the Democrat who placed second. If California did not have a top-two system, there would be a petition procedure for an independent candidate to get on the ballot, due in August; and there would be write-in space on the November ballot. But the top-two system in California eliminated the ability of anyone to get on the November ballot, except by placing first and second in the June primary. The top-two law also deleted write-in space from the November ballot.
Adam Nagourney of the Los Angeles Times has a story, “An indictment reveals a pitfall for the top-two system.” UPDATE: this San Diego Union-Tribune article gives more details. It explains that Republicans were worried about the possibility, and had entered another Republican in the June primary, but that other Republican did not get substantial funding and only placed third.