Trump was put over the top in the Associated Press delegate count by a small number of the party's unbound delegates who told the AP they would support him at the national convention in July. Among them is Oklahoma GOP chairwoman Pam Pollard.

"I think he has touched a part of our electorate that doesn't like where our country is," Pollard said. "I have no problem supporting Mr. Trump."

It takes 1,237 delegates to win the Republican nomination. Trump has reached 1,238. With 303 delegates at stake in five state primaries on June 7, Trump will easily pad his total, avoiding a contested convention in Cleveland.
    
Trump, a political neophyte who for years delivered caustic commentary on the state of the nation from the sidelines but had never run for office, fought off 16 other Republican contenders in an often ugly primary race.

Many on the right have been slow to warm to Trump, wary of his conservative bona fides. Others worry about his crass personality and the lewd comments he's made about women.

But millions of grass-roots activists, many of them outsiders to the political process, have embraced Trump as a plain-speaking populist who is not afraid to offend.

Steve House, chairman of the Colorado Republican Party and an unbound delegate who confirmed his support of Trump to the AP, said he likes the billionaire's background as a businessman.

"Leadership is leadership," House said. "If he can surround himself with the political talent, I think he will be fine."

Trump's pivotal moment comes amid a new sign of internal problems. Hours before clinching the nomination, he announced the abrupt departure of political director Rick Wiley, who was in the midst of leading the campaign's push to hire staff in key battleground states. In a statement, Trump's campaign said Wiley had been hired only on a short-term basis until the candidate's organisation "was running full steam."

His hiring about six weeks ago was seen as a sign that party veterans were embracing Trump's campaign.

A person familiar with Wiley's ouster said the operative clashed with others in Trump's operation and didn't want to put longtime Trump allies in key jobs. The person insisted on anonymity because the person was not authorised to publicly discuss the internal campaign dynamics.

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