The race for the Republican U.S. presidential nomination is now focused on and its January 31 primary election.

Polls say the top two candidates seeking to defeat President Barack Obama in November are former Massachusetts governor Mitt Romney and Newt Gingrich, a former speaker of the House of Representatives. Gingrich has the momentum after last week's upset victory over Romney and two others in another southern state, South Carolina.

Of the other two candidates, former Pennsylvania senator Rick Santorum calls Gingrich “erratic” and Romney a “moderate,” not a conservative. Texas Congressman Ron Paul says polls show he would do better against President Obama among young voters than any of his three opponents.

All four met in Tampa Monday for another debate.

Gingrich defended his four years as House speaker while Romney pointed out that Gingrich resigned for ethics violations when he lost the support of many of his fellow Republicans.

Santorum called himself the true conservative while Paul says he would not firmly rule out a run as a third party candidate if he loses the Republican nomination.