Mitt Romney continues to lead the pack of potential Republican challengers to President Obama in 2012, while more Democrats are starting to favor a new candidate. 

Romney has the support of 21 percent of respondents in a new CNN/Opinion Research poll released Friday. Sarah Palin was the respondents' second favorite at 18 percent and Newt Gingrich was third with 15 percent. The survey of close to 500 Republicans was conducted Aug. 6-10, which means it doesn't reflect any possible fallout from Marianne Gingrich's interview with Esquire magazine.

Meanwhile, former Arkansas Gov. Mike Huckabee fell from being the pack leader in April with 24 percent to getting only 14 percent in the new poll.

On the Democratic side, there was a slight uptick in respondents preferring a "different candidate" to Obama in 2012. Back in March, 20 percent said they would like a new nominee, while now 23 percent favor a candidate change. The White House has recently been engaged in a public war of words with the "professional left," but even his liberal critics doubt a candidate will step forward to launch a primary challenge to Obama.