This Sacramento Bee story says some well-funded Democratic interest groups are considering campaigning against some Democratic candidates for U.S. House in California, to lessen the chances that the top-two system will cause a complete absence of Democrats on the November ballot in some districts. Their fear is that too many Democratic candidates on the primary ballot means Democratic voters will split the vote, and put two Republicans on the November ballot. Thanks to California Politico for the link.
UPDATE: see this parallel story in the Los Angeles Times, which has more details. Thanks to Rick Hasen for that link.