SACRAMENTO, California — An ongoing federal investigation of a California senator is roiling the Democratic leadership in Sacramento and threatens to complicate relations in the majority party when lawmakers reconvene in January. FBI agents raided the offices of Sen. Ron Calderon in June, but the drama escalated within the past month when the Los Angeles-area lawmaker tried to tar his fellow Democrats after they stripped him of his committee assignments and one called for his resignation. Calderon has denied allegations he took money in return for promoting bills, but some analysts say the inquiry could affect the re-election chances for...