The CNN/ORC poll released Sunday suggested that Clinton, who became Obama's secretary of state after losing the Democratic presidential nomination to him in 2008, has an edge with a couple of significant groups.
"Politically speaking, there is an interesting group of people who would not vote for Obama but would pick Clinton over Romney," CNN Polling Director Keating Holland said. "It turns out that nearly seven in ten of them are women, and 56% are independents."
On the Republican side, there's a statistical five-way tie at the top. New Jersey Gov. Chris Christie, Sen. Rand Paul, R-Ky., and former Arkansas Gov. Mike Huckabee are at 12 percent, and Texas Gov. Rick Perry and Rep. Paul Ryan, R-Wis., are a 11.
Both Christie and Perry have jumped 5 points since CNN's last poll in June.
None of the possible candidates has declared yet, although some have made trips to Iowa and New Hampshire.
Clinton's standing with voters has edged down recently, during a period when she has been touting "Hard Choices," her new book. Stanton suggested that may be because the public now sees her as a likely candidate and not because of remarks she made in the book or on tour.
ORC International surveyed 1,012 likely voters by telephone between July 18 and July 20. The margin of error is 3 percentage points.