Found this J. Moore Methods poll over at Calitics. Lt. Gov. John Garamendi leads among likely voters (36% have no opinion). (Rupf is Republican Warren Rupf, Sheriff of Contra Costa County.)
Garamendi
Rupf
DeSaulnier
Buchanan
Support:
24
17
13
10
Known:
80
20
39
45
Favorable:
35
9
16
17
Unfavorable:
12
9
13
12
While Garamendi does have a commanding lead in the polls and the name rec, Senator Mark DeSaulnier or Assemblywoman Joan Buchanan can try and catch up, but it will be a long shot when facing Garamendi's high name rec and campaign war chest. DeSaulnier is a great progressive in the state legislature and I would like him to win, but no one knows if it will be enough. For now this race is Garamendi's to lose.