NEW YORK • Governor Scott Walker of Wisconsin, whose early glow as a Republican presidential contender was snuffed out with the rise of anti-establishment rivals, is quitting the race and urging some of his 15 rivals to do the same so that the party could unite against leading candidate Donald 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 United States electorate - Hispanics, women, immigrants, veterans and, most recently, Muslims - if Mr Trump continued vilifying or mocking those groups as part of his overtures to angry and disaffected voters.

Still, his exit was not a selfless sacrifice: He was running low on campaign cash, sliding sharply in opinion polls, losing potential donors to rivals and unnerving supporters with a stream of gaffes, like saying he would consider building a barrier wall along the Canadian border.

Appearing ashen and drained at a brief news conference on Monday, Mr Walker said the Republican presidential field was too focused on "how bad things are" rather than on "how we can make them better for everyone".

Without naming Mr Trump, he issued a plea to fellow candidates to coalesce around a different Republican who could offer a more "optimistic" vision and guide the party to a victory next year that, he admitted with sadness, he could not achieve himself.

"Today, I believe that I am being called to lead by helping to clear the field in this race so that a positive, conservative message can rise to the top of the field," he said.

"I encourage other Republican presidential candidates to consider doing the same so that the voters can focus on a limited number of candidates who can offer a positive, conservative alternative to the current front runner."

None of Mr Walker's rivals appeared poised to take him up on the suggestion of bowing out, though they expressed surprise he was withdrawing so soon.

"Holy cow," Senator Ted Cruz of Texas said on Fox News.

Mr Trump, in a Twitter post, was magnanimous: "I got to know @ScottWalker well - he's a very nice person and has a great future."

Mr Walker's departure is likely to have little effect given the sprawling field.

He got support from less than half of 1 per cent of Republican primary voters in a recent CNN national poll.

NEW YORK TIMES