Romney, the former Massachusetts governor, led the field with 24 percent, while Texas Gov. Perry was second with 20 percent, a Quinnipiac University poll released Wednesday said.
No other candidate captured more than 9 percent, results indicated.
Among all contenders, former Alaska Gov. Sarah Palin -- who hasn't indicated whether she'll enter the GOP race -- garnered 9 percent, followed by businessman Herman Cain at 7 percent, Rep. Ron Paul of Texas at 6 percent, and former Sen. Rick Santorum of Pennsylvania and former House Speaker Newt Gingrich at 4 percent each. Rep. Michele Bachmann of Minnesota was eighth with 3 percent.
If Palin doesn't run, Romney gets 25 percent to Perry's 21 percent, the Hamden, Conn., university said.
In a hypothetical general election match-up, Obama would get 44 percent to Perry's 41 percent, too close to call when factoring the margin of error, pollsters said. In an Obama-Romney tilt, the president would get 44 percent to Romney's 42 percent, also too close to call.
Results are based on telephone surveys of 1,301 registered voters from Sept. 20-25. The margin of error is 4.8 percent.