Democratic Sen. Hillary Clinton (NY) overtook Illinois Sen. Barack Obama in a hard-fought race, while former Massachusetts Gov. Mitt Romney coasted to an easy win in the Republican contest.
In the Democratic caucus, Obama ran a strong second, with former North Carolina Sen. John Edwards finishing a distant third.
Romney's rivals have been concentrating their efforts on the concurrent primary in South Carolina: a state that has consistently foretold the Republican nomination since 1980.
NPR's Scott Horsley gives the latest from Las Vegas.