Updated at 6:40 p.m.
Wisconsin Gov. Scott Walker ended his campaign for president Monday, capping off a rapid rise and equally rapid fall in the GOP race.
At a brief 6 p.m. ET press conference in Madison, Wis., Walker said he was suspending his White House bid, in part, to stop the current GOP front-runner Donald Trump.
"Today I feel I am being called to lead by helping to clear the field so that a positive, conservative message can rise to the top of the field," Walker said.