In the poll of self-identified Republican adults, Trump and Huckabee tied for first at 19%, followed by Palin at 12%, and Newt Gingrich and Mitt Romney at 11% each. Ron Paul placed sixth with 7%, and was trailed by Michele Bachmann (5%), Mitch Daniels (3%), Tim Pawlenty (2%), and Rick Santorum (2%).

Trump posted the biggest gain by far in the latest poll. One month ago, CNN pegged his support at 10%, good for fifth place. But since then, Trump has gone on a media blitz, appearing on cable news shows and repeatedly flogging old conspiracies on the long-since settled issue of President Obama's citizenship.

This is the second poll in as many weeks to show Trump giving the establishment candidates a run for their money. Last week, an NBC/Wall Street Journal poll showed Trump running in second place at 17%, just behind frontrunner Romney's 21%.

Romney fell furthest in the CNN survey since March, dropping seven points from his second place finish one month ago.