Trump, last man standing in Republican White House race, now has to unify party as Kasich bows out

Donald Trump became the last man standing in the race for the Republican US presidential nomination on Wednesday as one after the other his sole remaining rivals, Ted Cruz and John Kasich, faded out of the picture.

Anointed the presumptive nominee after winning Indiana on Tuesday, the 69-year-old New York billionaire turned to a new phase in his campaign, planning to set up a vice presidential selection committee and stepping up efforts to seek unity with more Republicans.

But the wounds from a brutal primary battle were still raw among many Republican loyalists who simply cannot bear to support Trump because they worry he could spell disaster for the party in the Nov 8 elections.

Kasich, the Ohio governor who stayed in the race in hopes of persuading Republicans to choose him as the nominee at a contested convention in July, made plans to get out of the race now that a contested convention has been averted.

News reports said Kasich would suspend his campaign, making it official in Columbus, Ohio, at 5pm EDT (2100 GMT).

Trump has overcome sustained opposition from Republican rivals by using his star power to give voice to an anti-establishment movement.

His supporters have been wildly enthusiastic about his "America First" platform, which has strayed far from some conservative bulwarks like free trade and military interventionism.

Trump's immediate challenge is to mend deep fissures within the Republican Party, easing tensions with party loyalists who have been appalled by his bombastic, bullying style, his denigrating comments about women and his proposals to build a wall on the border with Mexico and deport 11 million illegal immigrants.

In a series of Wednesday morning television interviews, Trump made clear he would not be looking to placate everyone after a tumultuous primary campaign in which many establishment Republicans rejected him and spawned Stop Trump and Never Trump movements.

"I am confident that I can unite much of it, some of it I don't want," Trump said on NBC's "Today" show.

"Honestly, there are some people I really don't want. People will be voting for me. They're not voting for the party."

Trump believes more Republicans will support him when they consider the possibility of Hillary Clinton, favourite to be the Democratic nominee, being elected president, Trump spokeswoman Katrina Pierson said.

"They're going to come around," she said on MSNBC.

The New York Times quoted Trump as saying he would soon form a team to help him in the search for a vice presidential nominee to be announced in July.

He put retired neurosurgeon Ben Carson on the committee. Carson endorsed Trump after pulling out of Republican race earlier this year.

US Republican presidential candidate Donald Trump speaks at a campaign event at The Palladium at the Centre for Performing Arts in Carmel, Indiana, May 2, 2016. Reuters

Republican US presidential candidate Donald Trump gets a kiss from his daughter Ivanka at the end of a campaign victory party after rival candidate Senator Ted Cruz dropped out of the race for the Republican presidential nomination following the results of the Indiana state primary, at Trump Tower in Manhattan, New York, May 3, 2016. Reuters

Trump, a former reality television star who has never held public office and who has honed an 'outsider' image, suggested he might make a more conventional choice as his running mate.

"I'm more inclined to go with a political person," Trump told the Times. "I have business very much covered."

Trump's win in Indiana cleared the way him to prepare for a likely match-up in the November general election against former Secretary of State Clinton.

She lost the Indiana primary to her tenacious challenger, US Senator Bernie Sanders, but remains on course to become her party's nominee.

'Unite and focus'

Republican National Committee Chairman Reince Priebus called Trump the party's presumptive nominee in a tweet on Tuesday night and said, "We all need to unite and focus" on defeating Clinton.

In an interview Wednesday, Priebus acknowledged achieving Republican unity would be difficult.

"It's going to take some time but we're going to get there," he said on CNN.

Republican Senator Deb Fischer of Nebraska made clear she would support the nominee but is not comfortable with Trump, in an interview with Nebraska Radio Network.

"Mr Trump is going to have to work hard to bring the party together," she said. "He's going to have to work hard to explain his stance on different issues and to talk about the principles and values he holds. I look forward to having a robust race here."

Support for Trump among Republicans nationally jumped in recent weeks to the highest level of the primary campaign, according to Reuters/Ipsos polling.

A recent poll found Trump with the support of 53 percent of Republican participants, well above Cruz at 25 percent. Kasich had 16 percent.

In a potential general election match-up, however, Clinton led Trump by about 10 percentage points among likely voters.

The poll included 623 Democrats and 556 Republicans and had a credibility interval of 5 percentage points.

Clinton called Trump a 'loose cannon' on Wednesday and said America should not take a risk on an unreliable candidate.

Since launching his White House bid last summer as a longshot amid a crowded field that included governors, former governors and US senators, Trump repeatedly defied predictions that his campaign would implode.

He prevailed over rivals he derided as "grown politicians", despite making provocative statements along the way that drew sometimes furious criticism from many in the party but fed his anti-establishment appeal.