Rick Santorum overwhelmingly won the Kansas presidential caucuses, hoping to blunt front-runner Mitt Romney’s momentum in the grinding campaign for the nomination to oppose President Barack Obama in the November election.
But Mr Romney countered with wins in Wyoming as well as in Guam, the Northern Mariana Islands and the US Virgin Islands.
Mr Santorum, a former Pennsylvania senator, was considered the favourite in Kansas, where his staunch opposition to abortion and gay marriage resonated with the state’s large bloc of evangelical voters.
He hoped his victory would give him an advantage heading into Tuesday’s unexpectedly pivotal primaries in the southern states of Alabama and Mississippi where polls show he is dividing the most conservative vote with Newt Gingrich.
Mr Gingrich, struggling for survival in the race, can ill afford a loss in either Mississippi or Alabama.
Mr Romney is seeking a Southern breakthrough to demonstrate an ability to win the support of evangelical voters.
For his part, Mr Santorum hopes to knock Mr Gingrich out of the race and finally emerge as Mr Romney’s sole challenger from the right.
Final returns in Kansas showed Mr Santorum with 51% support, far outpacing Mr Romney, who had 21%. Mr Gingrich had 14% and Ron Paul trailed with 13%.
Mr Santorum picked up 33 of the state’s 40 delegates at stake, cutting slightly into Mr Romney’s overwhelming advantage.
“Things have an amazing way of working out,” Mr Santorum told supporters in Missouri, where he traced his campaign through a series of highs and lows. He called his showing in Kansas a “comfortable win”.
In sparsely populated Wyoming, Mr Romney won seven of the 12 delegates at stake, Mr Santorum three, Mr Paul one. Uncommitted won one.