Donald Trump entered into a joint fundraising agreement with the Republican National Committee that will allow the presidential candidate to tap rich donors and end his ability to claim that he is self-financing his own campaign.
The Trump campaign and the RNC on Tuesday evening said they had agreed to create two joint fundraising committees, including one named the "Trump Make America Great Again Committee", and a second called "Trump Victory" to which single donors could donate up to $449,400.
The property developer said the deals would raise money for Republicans running in November, helping the party to "defeat Hillary Clinton, keep Republican majorities in Congress and in the states, and Make America Great Again".
Reince Priebus, RNC chairman, said the committees were a "vital step" towards protecting Republican majorities across America and would help boost "ground, data and digital operations to elect Republicans up and down the ballot".
Mr Trump can afford to focus his energy and money on hitting Mrs Clinton, as the former secretary of state continued to face a challenge from Bernard Sanders.
The Vermont senator beat his Democratic rival in the Oregon primary election on Tuesday night, while Mrs Clinton had a razor-thin lead with 46.8 per cent of the vote in Kentucky after 99 per cent of the ballots had been counted.
In Oregon, Mr Sanders was ahead with 53 per cent compared to 47 per cent for Mrs Clinton, based on two-thirds of the votes counted, and was projected by the Associated Press to win the state.
The victory repeats a pattern as Mr Sanders continues to frustrate Mrs Clinton and draws attention to some of her flaws as a candidate.
It also comes as some polls show that Mr Trump could pose a bigger threat to Mrs Clinton than many had previously expected.
The fundraising deal with the Republican party marks a major shift by Mr Trump who insisted during the primaries that he was different from other candidates as he was financing his own campaign and therefore could not be bought or corrupted.
But he has been forced to abandon that stance under the growing realization about the amount of money needed to run a national campaign, including paying for the kind of extensive grass roots operation needed to get out the vote across the US.
The agreement with the RNC also marks the latest thaw in frosty relations between Mr Trump and the party establishment, many of whom have been concerned about his divisive rhetoric during the primaries. Last week Mr Trump met Paul Ryan, the powerful Republican speaker of the House of Representatives — who has so far refused to endorse the billionaire — in an effort to improve ties with the mainstream party. While Mr Ryan made positive noises about their meeting, he made clear that it was too early to support Mr Trump by having "fake" unity.
The decision by Mr Trump to use more traditional financing comes as Super-Pacs — outside groups that support one candidate but cannot co-ordinate with the campaign — have started launching attacks against the tycoon. Priorities USA, one of the main groups backing Hillary Clinton, will on Wednesday start running hard-hitting attack ads on Mr Trump in the key swing states of Florida, Ohio, Virginia and Nevada.
The first ad, which was released online on Tuesday, attacks Mr Trump over his stance on women by repeating a number of his most controversial statements.
In the Republican race, Mr Trump was on course for an easy victory in Oregon after his two remaining challengers, Texas senator Ted Cruz and Ohio governor John Kasich, dropped out of the race following their losses in Indiana two weeks ago.
Although Mr Trump signed the fundraising deal with the GOP on Tuesday, he still faces significant resistance inside the party.
Many Republican elites, including former presidents George Bush and George W Bush and the 2012 Republican nominee Mitt Romney, have vowed not to support the tycoon, because of doubts about his conservative credentials and concern about his divisive rhetoric towards women, Hispanics and minority groups.
Since becoming the likely Republican nominee following his win in Indiana, Mr Trump has appeared to edge closer to the political centre and tone down his rhetoric slightly. But his critics argue that he lacks the temperament to occupy the Oval Office and serve as commander-in-chief. Those Republicans who have rallied around Mr Trump's campaign generally see him as the lesser of two evils and would rather see him in the White House than Mrs Clinton.