New Field Poll in California, Republicans only (August 3-12, 348 Republican LV). Giuliani still leads by a healthy margin, but Mitt Romney and Fred Thompson have moved into a tie for second place while John McCain's support in the Golden State has crumbled in the last five months:

Giuliani 35 (+1 vs. last poll in March)
Romney 14 (+7)
Thompson 13 (+5)
McCain 9 (-15)
Tancredo 3 (nc)
Hunter 2 (-1)
Undecided 20 (+5)

Also in the poll: Giuliani's support is stable among the 33% of likely Republican primary voters who say they are following the race "very closely," but his lead shrinks because both Romney and Thompson do better among this group:

Giuliani 34
Romney 21
Thompson 19
McCain 5
Others 8
Undecided 13

The poll also notes the following sub-group preferences:

- Giuliani's support is broad-based, and is 30% or more across all major GOP voting blocs.

- Support for Romney is greater among older voters and those who are not born-again Christians.

- Thompson does somewhat better among men, born-again Christians, and those likely to vote by means of an absentee ballot.