What's next as Republicans declare Trump their 'presumptive nominee' with Haley's exit

Former President Donald Trump is now the last major candidate standing in the Republican presidential primary field after rival Nikki Haley suspended her own campaign in the wake of a string of Super Tuesday losses.

That means Trump has essentially clinched the Republican nomination for president in the 2024 race -- though he's still days away from winning enough delegates -- setting up a rematch between himself and President Joe Biden in November.

The Republican National Committee declared him the party's "presumptive nominee" in a statement on Wednesday.

Reacting to the news of Haley suspending her campaign, Trump took another shot at her and labeled her supporters as "Radical Left Democrats" before inviting them "join the greatest movement in the history of our Nation."

Haley has argued that Trump can't win in a general election because he's losing too many Republican voters.

"It is now up to Donald Trump to earn the votes of those in our party and those beyond it to support him," she on Wednesday as she ended her 2024 bid. "I hope he does that."

Trump has played that argument down.

"Oh they'll vote for me again, everybody. And I'm not sure we need too many. I'm not sure," he told reporters in New Hampshire before that state's January primary. "I think that Biden is the worst president in the history of this country. But ... they're all coming back."

With Haley out of the race and the general election fully in view, Trump is also pushing for an overhaul of the RNC at a party gathering later this week in Houston where current Chairwoman Ronna McDaniel and the co-chair, Drew McKissick, are expected to resign from their positions, clearing the path for Trump-endorsed Michael Whatley and Lara Trump, the former president's daughter-in-law, to replace them.

Donald Trump has called them "highly talented, battle-tested, and smart."

Chris LaCivita, a Trump senior campaign adviser who is set to serve as the RNC's chief operating officer, said his primary focus of the party committee will be election integrity, one of Trump's central campaign issues as he continues to spread baseless claims about the 2020 race that he lost.

"Now that we get in there, this is not our first rodeo, so we have a pretty good idea of what we want to do," LaCivita told reporters at Trump's Super Tuesday watch party. "First and foremost it's about putting together real ground game operations that are built around early states."

One of the biggest advantages of Trump merging his campaign operation with the RNC is expected to be their joint ability to raise money, as both the Trump campaign and the party committee lag behind their respective Democratic counterparts that are raising together.

During the 2020 presidential election cycle, the Trump campaign and the RNC were together raising hundreds of millions of dollars a quarter, their joint fundraising operation with various local party committees allowing them to rake in north of $800,000 per donor.

Top Trump campaign officials wrote in a memo released last month that the campaign and the RNC should begin "convention planning, fundraising, strategy, and state party tactics" with the top Republican congressional campaign groups as soon as possible, as should their fight for the general election.

Lara Trump said that "every penny" of the party's funds should be prioritized toward Donald Trump's reelection, but his campaign insists that RNC funds would not be used to cover his legal fees -- a point that has been controversial among some Republicans.

Haley has decried Lara Trump becoming a key leader of the national Republican Party, warning over the weekend that if he succeeds "the RNC now is just going to be about Donald Trump" and would morph into his own "legal slush fund."

Several sources familiar with the matter confirmed to ABC News that a draft resolution that would prevent the RNC from covering Donald Trump's legal fees has died.

The resolution failed to garner enough support from enough states to bring to a vote in Houston.

LaCivita, the Trump adviser, confirmed to ABC that there was no longer a standing resolution. He also reiterated his "emphatic point" that a reworked national party would not be paying Trump's millions of dollars in legal bills.

After Haley announced she was suspending her campaign on Wednesday morning, Trump called for Haley supporters to coalesce behind him. But over the last couple months, Trump has been disparaging Haley and her supporters, even saying Haley's donors from now on would be "permanently barred from the MAGA world" after she continued on with her campaign after her New Hampshire defeat -- though Trump's campaign and fundraisers downplayed the comment, saying it's not likely going to be strictly enforced.

Haley, who in recent days has suggested that she no longer feels bound by an RNC pledge that would obligate her to support the eventual GOP nominee, did not endorse Trump while ending her campaign.

On Monday, Trump said he doesn't care if Haley is not committed to support him, going on to suggest she's irrelevant and not newsworthy.

Trump has already been focusing much of his attention this primary cycle on President Biden; however, now with officially no big Republican challengers remaining, the Trump campaign now says their focus is "100%" on the general election.

In his attacks, Trump has taken specific aim at Biden's immigration and economic policies, criticizing him for the withdrawal from Afghanistan and the current situation at the southern border and blaming him for high inflation. He has also made disparaging towards Biden about his mental acuity

The Biden campaign has centered its message on threats to democracy, pointing to Trump's attempts to overturn the 2020 election. In a memo sent to reporters, Biden's campaign indicated they may make an attempt to appeal to Haley supporters who tended to be relatively more moderate or independent voters.

"Primary after primary has exposed deep divisions among Republicans to Donald Trump's detriment — particularly with moderate and suburban voters who will be critical to victory in November," the campaign chair, Jen O'Malley Dillon, and campaign manager Julie Chavez Rodriguez wrote.

Biden then reaffirmed that pitch in a statement, saying "there is a place for them in my campaign."

Looking toward the general election, Trump will have to continue to split his time between the campaign trail and the courtroom as the first of his four expected criminal trials -- the hush money case in New York -- is expected to start later this month. He denies all wrongdoing.

"We'll just have to figure it out," Trump said outside a New York courtroom last month. "I'll be here during the day, and I'll be campaigning during the night."

ABC News' Nicholas Kerr contributed to this report.