SACRAMENTO, Calif. (AP) – A single state Senate race could determine if Democrats win a veto-proof two-thirds supermajority in the California Legislature. Democrats have an 18-point voter registration advantage in the 12th Senate District west of Fresno. Yet Republicans have held the seat. It’s open due to term limits and Republicans hope to keep it with a victory by Madera County Supervisor Rob Poythress. If they succeed on Tuesday, it could leave Democrats one vote short of a supermajority that would let them raise taxes, suspend legislative rules or override vetoes without Republican votes. Poythress is opposed by Assemblywoman Anna Caballero, a moderate Democrat who says her positions are a good fit with the agricultural district. Democrats are expected to retain a supermajority in the Assembly.