U.S. Republican presidential hopefuls are busy campaigning in Iowa Thursday, five days before the first nominating contest of the 2012 presidential campaign.

The candidates are filling the next several days with visits to local pizza joints, breakfast spots, and bars, rallies and town halls, and in between, speeding around the central U.S. state to their next campaign stop an hour or two or three later.

The latest Iowa poll shows Massachusetts Governor Mitt Romney is back on top and Representative Ron Paul is in second place. But former Senator Rick Santorum says he remains confident the caucuses, seen as an important indicator of nationwide prospects, will turn in his favor.

Santorum says his surprising surge to third place in the latest survey is because the voters there have met him and seen he reflects their values.

Still other candidates, faring less well in Iowa, are turning their attention to other states.

Former Speaker of the House Newt Gingrich, the latest favorite to fade away, has tumbled into fourth place in Iowa after a barrage of negative advertising from rival campaigns. Though he continues to campaign hard in the testing ground state, Gingrich reminded reporters the candidate will be chosen in votes in 50 states, not just one, and said in many other states he retains a strong lead.

And Jon Huntsman, who was President Barack Obama's ambassador to China, is focusing instead on New Hampshire, the second state scheduled to vote on a nominee.

In the latest survey in that state, Romney holds a strong lead, supported by 44 percent of likely primary voters, followed again by Paul.