This is interesting. It seems that Feinstein is being credibly challenged from the left:

The California Democratic Party denied U.S. Sen. Dianne Feinstein an endorsement at its state convention Saturday, a sign of liberal discontent with the establishment among grassroots members.

Ms. Feinstein’s opponent, Kevin de León, president pro tempore in the state Senate, captured 54% of the vote among delegates here. Sixty percent of the votes were needed to capture the party’s official endorsement ahead of the June 5 primary.