The latest U.S. political poll shows the rankings have shifted again among Republican presidential hopefuls, with less than a week to go before the Iowa caucuses and the official start of the 2012 presidential campaign.

Former Massachusetts governor Mitt Romney is back on top in the latest figures, Wednesday, with Ron Paul in second place.

In Iowa, scheduled to hold caucuses January 3 to choose its nominee, former Massachusetts Governor Mitt Romney and U.S Congressman Ron Paul of Texas are just a few points apart. And in a surprise surge, former Pennsylvania senator Rick Santorum has almost tripled his support, climbing to third place state.

In New Hampshire, the second state scheduled to vote on a nominee, Romney holds a strong lead, supported by 44 percent of likely primary voters, followed again by Paul.

And in both states former House of Representatives speaker Newt Gingrich has become the latest favorite to fade away. After a barrage of negative advertising from rival campaigns, Gingrich has tumbled into fourth place in Iowa and third place in New Hampshire.