Thompson Stalls in California

The latest poll from SurveyUSA:

Seven months before the newly accelerated and suddenly critical California Republican Primary, the contest re-stabilizes, with Rudolph Giuliani 13 points ahead of John McCain and Fred Thompson, who tie for 2nd place, according to a SurveyUSA poll of likely GOP Primary voters, conducted exclusively for KABC-TV Los Angeles, KPIX-TV San Francisco, and KGTV-TV San Diego. Giuliani's 13-point advantage today is identical to his lead 60 days ago, in SurveyUSA's May 2007 tracking poll, and a slight increase from the 7-point advantage Giuliani had in June. Fred Thompson, who went from 11 points in May to 21 points is June, has stopped climbing, and settles in at 19 points in July. Is this Thompson's ceiling? Or has Thompson, whose official entry into the race may come at any moment, not yet begun to fight?