New poll results released on Monday showed former U.S. House speaker Newt Gingrich on top of the GOP field and benefiting from the exit of Herman Cain from the presidential campaign, leading runner-up Mitt Romney by double digits in the GOP race.

U.S. Republican presidential contender Herman Cain announces on Saturday that he has decided to suspend his presidential campaign. [Xinhua/AFP]

The Poll Position poll is the first national public opinion survey on the U.S. Republican presidential nomination contest since Cain suspended his campaign on Saturday. It finds among likely 2012 Republican primary and caucus voters, Gingrich leads Romney by a 37 percent to 23 percent margin, with Ron Paul at 7 percent, Michele Bachmann 6 percent, Rick Perry 3 percent, Jon Huntsman 2 percent, and Rick Santorum 2 percent.

A week ago, another Poll Position GOP horse race survey found Gingrich at 32 percent, Romney 23 percent, and Cain at 14 percent.

The latest survey was conducted on Sunday night. It questioned 502 registered voters nationwide, who said they would vote in their states' Republican primary or caucus. The poll has a margin of error of 4 percent.

Cain dropped out of the race on Saturday, saying allegations of sexual harassment and infidelity against him were hurting his family. He said he will make an endorsement soon. Media reports said he might endorse Gingrich.