SAN DIEGO — In a sharp rebuke to Sen. Dianne Feinstein, the California Democratic Party has declined to endorse the state’s own senior senator in her bid for reelection.

Riven by conflict between progressive and more moderate forces at the state party’s annual convention here, delegates favored Feinstein’s progressive rival, state Senate leader Kevin de León, over Feinstein by a vote of 54 percent to 37 percent, according to results announced Sunday.