WASHINGTON — Former pizza chain executive Herman Cain has surged in the race for the Republican presidential nomination and is hot on the heels of frontrunner Mitt Romney, a new Gallup opinion poll showed Monday.

Romney, a former Massachusetts governor, led the crowded field with 20 percent of Republicans and Republican-leaning independents saying they backed him to take on President Barack Obama in the November 2012 elections.

But the survey found Cain has tripled his support from mid-September and now stands at 18 percent, while Texas Governor Rick Perry has seen his own support cut by roughly half to 15 percent.

And the poll found an unusually large segment of Republican voters -- 20 percent -- still undecided, the latest sign of party unhappiness with the contenders to be the party's standard-bearer in 13 months.

The Gallup survey, which questioned a random national sample of 1,064 Republicans and Republican-leaning independents of voting age last week, had an error margin of plus or minus four percentage points.

National polls are solid barometers of voter mood, but the fight for the Republican nomination will be a state-by-state affair, dampening their predictive value.

Representative Ron Paul was at eight percent, former House speaker Newt Gingrich was at seven percent, Representative Michele Bachmann was at five percent, former senator Rick Santorum was at three percent, and former US envoy to China Jon Huntsman was at two percent, according to the poll.

Photo credit: Matthew Reichbach