The latest Public Politic Polling indicated Obama is tied with former Massachusetts Gov. Mitt Romney at 45 percent, the same as last month.
Included in the mix for the first time, Perry trailed Obama by 6 percentage points, 49 percent to 43 percent, results indicated. U.S. Rep. Michele Bachmann of Minnesota lost some ground between surveys, trailing 50 percent to 42 percent, down from a 48 percent-to-41 percent showing in July.
Herman Cain slipped to 49 percent to 39 percent from a 48 percent-to-36 percent tally, the Raleigh, N.C., polling agency said.
Former Alaska Gov. and Fox News commentator Sarah Palin, who hasn't tipped her hand, trailed Obama 53 percent to 37 percent in the latest poll, up slightly from a 53 percent-to-40 percent margin previously.
"Rick Perry's momentum in the Republican field is the best thing that's happened to Barack Obama lately," said Dean Debnam, Public Policy Polling president. "The president would have an easier time winning re-election against him than Mitt Romney."
Results are based on a nationwide survey of 700 voters Thursday through Sunday. The margin of error is 3.7 percentage points.