PRINCETON, NJ -- Initial indications show support for John McCain is increasing following his win in the Florida presidential primary and the subsequent withdrawal of Rudy Giuliani, who endorsed McCain. Gallup Poll Daily tracking data from Jan. 28-30 shows McCain with a 15-percentage point lead over Mitt Romney. McCain is the top choice of 37% of Republican voters nationwide, compared with 22% for second-place Mitt Romney. In Wednesday's release, the gap between McCain and Romney was 11 points (32% and 21%, respectively). Mike Huckabee is holding steady in third place at 17% in the current numbers. Giuliani was included in the Jan. 28 and 29 interviewing, but removed from the ballot last night. The one-night interviews from Jan. 30 -- with Giuliani out of the race -- show a substantial increase in McCain's support, suggesting his lead will likely expand in the coming days. Wednesday night's interviewing also was the first conducted following McCain's win Tuesday in Florida.

The latest Democratic numbers show Hillary Clinton with a 43% to 39% advantage over Barack Obama among Democratic voters nationwide. That four-point lead is the narrowest since early January, and it is a continuation of gains by Obama. The impact of John Edwards' exit from the Democratic race is less clear. Wednesday night's numbers (the first with Edwards excluded from the ballot) show no clear indication that either candidate is benefiting disproportionately. Clinton and Obama will debate in California tonight, which could affect Democrats' support for the two candidates going into the weekend before Super Tuesday's primaries and caucuses. -- Jeff Jones

Methodology: Gallup is interviewing 1,000 U.S. adults nationwide each day during 2008. The results reported here are based on combined data from Jan. 28-30, 2008, including interviews with 1,020 Republican and Republican-leaning voters and 1,286 Democratic and Democratic-leaning voters. For results based on these samples, the maximum margin of sampling error is ±3 percentage points. In addition to sampling error, question wording and practical difficulties in conducting surveys can introduce error or bias into the findings of public opinion polls.