Rick Santorum won Kansas on Saturday in the arduous race for the Republican presidential nomination, easily disposing of his rivals in a state where two of them didn't bother to compete.

Final returns in Kansas showed Santorum, a staunch social conservative and former Pennsylvania senator, had 51 per cent of the vote in the Kansas caucuses. Mitt Romney, the current delegate leader and perceived front-runner, came in second with 21 per cent while Newt Gingrich and Ron Paul duked it out for third place.

Only Santorum and Paul campaigned for the 40 delegates in Kansas, the so-called Sunflower State, where Christian evangelicals make up a third of the population and there's a long history of social conservative activism.

It was a different story In Wyoming, where Romney won the battle for its 12 delegates; the former Massachusetts governor also boosted his delegate count overnight when he won nine delegates each on the island of Guam and in the Northern Mariana Islands.

Delegate count

  • Romney — 453.
  • Santorum— 217.
  • Gingrich — 107.
  • Paul — 47.

A candidate must win 1,144 to clinch the Republican presidential nomination at the party's national convention in August.

The Kansas and Wyoming contests represent a prelude to Tuesday's primaries in Alabama and Mississippi, contests that have taken on a new significance in the Republican race.

Part of Santorum's comeback strategy has involved a decisive victory in Kansas that he hopes will propel him to big wins in Alabama and Mississippi. A combined 90 delegates are at stake in the southern primaries.

"This is definitely a good day for the campaign," Santorum spokesman Hogan Gidley said in a release on Saturday following Santorum's Kansas victory. "We're the only ones that have proven we can win all over this country."

Fresh attacks ahead of Alabama

However, Gingrich, has a narrow lead over Santorum and Romney in Alabama in a tight three-way race. And a fresh Mississippi poll has Santorum trailing Gingrich and Romney in the state.

'What other crazy "Washington" ideas does Rick Santorum have planned for America?'— Mitt Romney attack ad

Romney's so-called Super PAC has been fighting hard against Santorum in Alabama, distributing flyers in the mail that reiterate previous attacks on his rival for supporting the restoration of voting rights to convicted felons.

"Rick Santorum voted with Hillary Clinton to allow felons to vote. Even as a Washington insider, Rick Santorum should know this is wrong," reads the pamphlet, adorned with an illustration of an apparent felon in orange prison garb bowing his head.

"You know Rick Santorum has been in Washington too long when he keeps putting his interests ahead of ours. What other crazy 'Washington' ideas does Rick Santorum have planned for America?"

Gingrich is rejecting pressure from the Santorum campaign to quit the race and free up his socially conservative delegates. On Friday, the former speaker of the House of Representatives asserted he'd stay in the race until the party convention in Florida in August, even if he loses Alabama and Mississippi.

"We'll clearly do well enough to move on, and I think there's a fair chance we'll win" in Mississippi and Alabama, Gingrich told The Associated Press. "But I just want to set this to rest once and for all: We're going to Tampa."

Gingrich's press secretary has said that Gingrich needs to win both southern states to remain a viable candidate. "From Spartanburg to Texas, those all need to go for Gingrich," R.C. Hammond said last week.