Rounding out the GOP field are businessman Herman Cain (6 percent); former House Speaker Newt Gingrich (5 percent); Rep. Ron Paul, R-Tex. (5 percent); former Minnesota Gov. Tim Pawlenty (3 percent); former Sen. Rick Santorum, R-Pa., (1 percent), former Utah Gov. Jon Huntsman (1 percent); and Rep. Thaddeus McCotter, R-MIch., (less than 1 percent).
Each Republican trails in general election matchups against President Obama among all registered voters, however. Romney trails Obama, 47 percent to 41 percent, unchanged from early June. Obama also leads Bachmann, against whom he was not previously tested, 50 percent to 38 percent.
Obama also posts leads over Palin (53 percent to 34 percent) and Perry (50 percent to 37 percent).
Voters, however, are split evenly on re-electing Obama. Equal percentages -- 47 percent -- say he deserves re-election and doesn't deserve re-election. That is virtually unchanged since early June.
The Quinnipiac poll surveyed 2,311 registered voters from July 5-11. The margin of error is +/- 2 percent. There were 913 Republicans and Republican-leaning independents; those results carry a margin of error of +/- 3.2 percent.