Donald Trump is taking his first steps towards a full-fledged general election campaign, moving to unite a fractured Republican Party behind him and begin raising the money needed for a national race.
Mr Trump began to reach out to party heavyweights, including making efforts to repair his at-times strained relationships with the Republican National Committee (RNC) and party donors.
A spokesman for George W Bush said the former president does "not plan to participate in or comment on" the 2016 presidential race.
The spokesman was responding to a media inquiry about whether Mr Bush planned to support Mr Trump.
While Bush has largely stayed out of politics since leaving the White House, his refusal to publicly support his party's nominee is remarkable. It underscores the deep frustration within some corners of the Republican party over Mr Trump's candidacy.
His father, former president George HW Bush, also has not been heard from since Mr Trump's string of victories in the north-east primaries and Indiana.
His campaign also named Steven Mnuchin as its national finance chairman on Thursday, saying in a statement that "he brings unprecedented experience and expertise to a fundraising operation that will benefit the Republican Party and ultimately defeat Hillary Clinton".
Mr Mnuchin is chairman and chief executive officer of Dune Capital management LLC, a private investment firm, and previously worked at the New York bank Goldman Sachs.
The process begins just days after Mr Trump's final two intra-party foes, Ted Cruz and John Kasich, suddenly dropped out, clearing his path to the nomination - as members of the celebrity businessman's campaign were set to meet with the RNC and enter a joint fundraising agreement needed for both his bid and Republicans to maintain control of Capitol Hill, aides said.
"In order to really govern, we need majorities in the House and Senate. We're going to work with the party to raise money for down-ballot races to be successful," said Corey Lewandowski, Mr Trump's campaign manager, in an interview on Thursday morning. "Mr Trump has agreed to be available to raise money."
"We're going to with work with the RNC hand-in-glove," Mr Lewandowski said.
Mr Lewandowski said that a fundraising plan has not yet been set for Mr Trump's White House bid, a hugely expensive undertaking even for a billionaire real estate developer. But Mr Trump himself acknowledged that he would have to sell some of his holdings to muster the hundreds of millions of dollars needed to self-fund.
"I mean, do I want to sell a couple of buildings and self-fund? I don't know that I want to do that necessarily," Mr Trump said on MSNBC on Wednesday.
Mr Trump starts out in a deep hole when it comes to fundraising.
As a primary candidate, he prided himself on not soliciting donations and never built a traditional fundraising operation with a finance team that can fan out across the country and raise quick cash for his bid.
Through the end of March, Mr Trump had raised $12m mostly from fans who clicked the "donate" button on his website or bought wares such as the ubiquitous red ballcap emblazoned with his slogan, "Make America Great Again," campaign finance documents show. He also made about $36m in personal loans to his primary campaign.
The contrasts starkly with Mrs Clinton, who has raised some $187m so far and began her general election fundraising effort back in November by setting up a "victory fund" that can solicit huge cheques for her campaign, the Democratic National Committee and state parties.
Mrs Clinton is spending the better part of this month on a fundraising spree that includes stops in New York, Michigan, California and Texas. Mr Trump, as of Wednesday night, had not a single fundraiser on the books.
The differences do not end there. A pro-Clinton super political action committee that can take unlimited donations from wealthy individuals, companies and unions has already reserved some $90m of advertising for the general election. Great America, which is shaping up to be the main pro-Trump super PAC, was almost $1m in debt as of the end of March.
Ed Rollins, who ran Ronald Reagan's 1984 campaign, hopes to change that. He joined Great America as a senior strategist and said on super PAC conference call on Wednesday that Mr Trump needs all the help he can get with finances. "We're going to figure out what the Trump campaign needs and can't do by itself," Mr Rollins told callers.
Mr Trump's lean campaign team, caught by surprise by the sudden end of the primary process, will likely soon expand and lean heavily on the RNC infrastructure as Mr Trump begins eyeing his November showdown with Mrs Clinton, though that would not fully happen until he officially becomes the nominee in July.
Aides said he also plans to soon begin preparing for the national party convention in Cleveland - "You'll see a very different type of convention this year," Mr Lewandowski said - as well as naming a transition team and a vice-presidential search committee.
Mr Trump has said he has not truly begun the VP vetting process - in four different interviews on Wednesday he gave four different answers as to whether he had consider Mr Kasich - but has said that he would favour a Washington veteran.
"Mr Trump would need someone to help govern in Washington, DC," Mr Lewandowski said. "When a complete outsider is picked to lead the ticket, it makes sense to have someone with government experience on it. He wants a strong executive who has a leadership role in DC."