LOS ANGELES — This would seem a moment of great opportunity for California Republicans. The state has become a national symbol of fiscal turmoil and dysfunction, the Legislature is nearly as unpopular as Congress and Democrats control every branch of government. But instead, the state party — once a symbol of Republican hope and geographical reach and which gave the nation Ronald Reagan (and Richard M. Nixon) — is caught in a cycle of relentless decline, and appears in danger of shrinking to the rank of a minor party. “We are at a lower point than we’ve ever been,” said...