Sen. John Thune (R-S.D.) said Wednesday evening he is not running for president in 2016.
Thune had also been seen as a likely candidate in 2012 before he ruled out a bid.
GOP Sens. Ted Cruz (Texas), Rand Paul (Ky.) and Marco Rubio (Fla.) are all seen as potential candidates for the GOP presidential nomination.
Thune, the Republican Conference chairman, was considered a potential 2012 hopeful before announcing, early in the process, that he would not run. In 2011, he said he decided against a run because he feared he would not be able to raise enough money to compete and did not want to let his Senate duties lag.
Late last year, Thune left the door open slightly to a 2016 run, saying you don't "ever rule out anything in politics."
Even earlier, however, in February of 2013, he said he wasn't planning a bid when asked by an elementary school student.
"Do I plan on running for president?” Thune asked. “I don't. I enjoy the job I have. And being the president is a very, very hard job."