By Steve Holland
WASHINGTON (Reuters) - Donald Trump is facing pressure to adopt a more presidential tone in his White House campaign from Republican supporters worried that a string of missteps may do him lasting damage in the remaining state contests needed to clinch the nomination.
Trump lost ground on the online prediction market after drawing fire for his suggestion, later dialed back, that women be punished for getting abortions if the procedure is banned and for asserting that as president he might loosen the ties with longstanding U.S. allies.
Those who marveled at Trump's rise are warning the front-running New York billionaire that his shoot-from-the-lip approach to campaigning could jeopardize his chance to win the Republican nomination to the Nov. 8 election.
Tuesday could be a turning point when Wisconsin hosts its nominating contest. Trump, 69, trails his leading rival, U.S. Senator Ted Cruz, 45, of Texas in the Upper Midwestern state.
A Cruz win would make it harder for Trump to reach the magic number of 1,237 delegates needed to secure the nomination before the Republican national convention in July. The winner will take all of Wisconsin's 42 delegates.
"If he continues to fumble the ball, he risks everything," said David Bossie, who as president of the conservative group Citizens United has helped to introduce Trump to grassroots activists. "These types of ham-handed mistakes give his opponents even greater opportunity."
TRUMP, PARTY TALK UNITY
A businessman and former reality TV show host, Trump has never held public office but hails his mastery of negotiating business deals as the sort of experience a U.S. president needs to be successful at home and abroad.
He sent ripples through the Republican Party, which promotes a muscular foreign policy, by declaring NATO obsolete and suggesting Japan and South Korea might need to develop nuclear weapons to ease the U.S. financial commitment to their security.
Trump made a surprise visit on Thursday to the Republican National Committee in Washington where he said he and chairman Reince Priebus discussed how to unify the party going into the July convention.
Priebus also addressed any confusion Trump may have had about delegate allocation rules that will govern the proceedings, a source familiar with the meeting told Reuters.
Should Trump fail to win enough delegates to secure the nomination outright in the state-by-state contests ending in June, party delegates will select a nominee at the convention in a complex process of sequential votes.
Online predictions market PredictIt said on Friday that the probability Trump will win his party's nomination had dropped sharply in the past week while the likelihood of a contested convention to choose another candidate had risen.
CAMPAIGN STYLE A RISK
Those Republicans who see in Trump a chance to generate voter turnout beyond party regulars to blue-collar Democrats and win the White House say his detail-free style of campaigning has come back to haunt him and he needs to gear up for a new phase.
Trump needs to be less sensitive about attacks from opponents and let some go by without responding, said retired neurosurgeon Ben Carson, a former Republican presidential candidate who dropped out of the race earlier this year and endorsed Trump.
"If he can just get beyond that and learn how to bite his tongue and redirect people to something that is important, it will show a level of statesmanship," Carson said.
During the Wisconsin campaign, Trump has relentlessly attacked Wisconsin Governor Scott Walker, who dropped out of the presidential race last year and who has endorsed Cruz.
Former U.S. House of Representatives Speaker Newt Gingrich, who has offered Trump informal advice, said Trump should replicate the type of performance he gave at the American Israel Public Affairs Committee on March 21, when he spoke from a teleprompter and offered a well-thought-out case for strong U.S.-Israeli relations.
Gingrich said Trump should make eight to 10 policy speeches in order to give voters "a sense of stability and seriousness."
"He's gone from being an insurgent that people laughed at and a front-runner that people were amazed by to the potential nominee. That requires you to change your role as all this comes together," Gingrich said.
Alternatively, Trump could also start to listen to what he says is his wife Melania's longtime admonishment, "Darling, be more presidential."
Former Secretary of State Hillary Clinton and U.S. Senator Bernie Sanders will compete in Wisconsin on Tuesday on the Democratic Party side. Both have hopscotched between Wisconsin and New York, which holds an April 19 primary.
Clinton, a former U.S. senator from New York with national campaign headquarters in Brooklyn, is trying to prevent the Brooklyn-born Sanders, who represents Vermont in Congress, from eroding support on her home turf. Both candidates will attend a state party fundraising dinner in Wisconsin on Saturday.
(Reporting by Steve Holland; Additional reporting by Amanda Becker; Editing by Howard Goller)