Republican Senator John Thune, long seen as a rising political star and possible White House contender, announced on Tuesday he will not run for president next year.
"At this time, I feel that I am best positioned to fight for America's future here in the trenches of the United States Senate," he said in a statement.
Thune gained attention in 2004 when he won his Senate seat by defeating the then-Senate Democratic leader, Tom Daschle, in their home state of South Dakota. Daschle became the first Senate leader in a half century to be voted out of office by his own constituents.
Among those Republicans still considering taking on President Barack Obama next year are former Massachusetts Governor Mitt Romney, former House Speaker Newt Gingrich and 2008 Republican vice presidential nominee Sarah Palin.
No one Republican hopeful has stood out so far as the most likely candidate for 2012.
Thune, 50, easily won a second Senate term last year.
With boyish good looks, the dark-haired, 6-foot-4-inch Thune, a member of Republican leadership, has been viewed as a possible national political figure.
"If I looked like John Thune, I'd be president of the United States today," Senator John McCain, the failed 2008 Republican presidential nominee, has quipped.
Thune became the second conservative Republican in Congress who has decided against seeking the party's 2012 presidential nomination, following Representative Mike Pence of Indiana.