Gov. Scott Walker of Wisconsin withdrew from the 2016 Republican presidential race on Monday, citing a need to “clear the field” for a “positive conservative message.”

Updated, 9:59 p.m. | Gov. Scott Walker of Wisconsin, whose early glow as a Republican presidential contender was snuffed out with the rise of anti-establishment rivals, announced Monday that he was quitting the race and urged some of his 15 rivals to do the same so the party could unite against the
leading candidate, Donald J. Trump.

Mr. Walker’s pointed rebuke of Mr. Trump gave powerful voice to the private fears of many Republicans that the party risked alienating large parts of the electorate — Hispanics, women, immigrants, veterans, and most recently, Muslims — if Mr. Trump continued vilifying or mocking them as part of his overtures
to angry and disaffected voters.