President Joe Biden speaks during a meeting of his Competition Council to announce new actions to lower costs for families in the State Dining Room of the White House in Washington, March 5, 2024. (PHOTO / AP)

NEW YORK - Democrat Joe Biden and Republican Donald Trump are scrambling to win over supporters of Nikki Haley, a constituency that could be crucial to sending either man back to the White House.

Haley dropped out of the Republican presidential nomination contest on Wednesday but did not endorse Trump and said it was now up to him to "earn" the support of voters who did not initially back him.

Republican presidential candidate former UN Ambassador Nikki Haley takes the stage to speak at a caucus night party in West Des Moines, Iowa, Jan 15, 2024. (PHOTO / AP)

Almost 570,000 voters in three key battleground states - Nevada, North Carolina, and Michigan - voted for Haley in the Republican nominating contest, a small but potentially significant group in races that have been decided by tiny margins in recent elections.

Haley won 250,000 votes in North Carolina's primary, for example, a state that Trump won by less than 75,000 votes in 2020.

Political strategists believe a significant number of Haley voters were Democrats or Democratic-leaning independents who crossed over to vote in Republican primary contests, to try to deliver a blow to Trump

Both Biden and Trump quickly put out statements on Wednesday calling on Haley voters to join their team - although they used vastly different tactics.

Biden commended Haley on "speaking the truth" about Trump, while Trump said he had "trounced" her in the Super Tuesday Republican contest.

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"Donald Trump made it clear he doesn't want Nikki Haley supporters. I want to be clear: There is a place for them in my campaign," Biden said in a statement.

In his Truth Social post, Trump added that he "would further like to invite all of the Haley supporters to join the greatest movement in the history of our Nation," and described Biden as an enemy who is destroying the country.

Trump has derided Haley throughout the campaign - including using sexist and racist language. And many of her voters have wondered if they still have a place in the Republican Party, which has coalesced around Trump, despite his repeated lies about having won the 2020 election against Biden, and the Jan 6, 2021, riot at the US Capitol.

Still, some experts say there's little precedent for Republicans like Haley's supporters to automatically come out for a Democrat in a general election.

"The next several months are going to be about the two candidates trying to convince people to come home to their regular party," said Hans Noel, an associate professor of government at Georgetown University.

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"Right now, the numbers are really high for Haley voters to say 'I would never vote for Trump.' But almost certainly most of them will come around and either vote for Trump or they might not vote at all," he said, citing historical precedent.

Political strategists believe a significant number of Haley voters were Democrats or Democratic-leaning independents who crossed over to vote in Republican primary contests, to try to deliver a blow to Trump.

Republican presidential candidate former President Donald Trump speaks at a Super Tuesday election night party, March 5, 2024, at Mar-a-Lago in Palm Beach, Florida. (PHOTO / AP)

Still, a bevy of anti-Trump groups will be working hard to convince Haley voters to get behind Biden.

Reed Galen, a co-founder of the Lincoln Project, a prominent anti-Trump group of current and former Republicans, said Haley had shown that there are up to 30 percent of Republican voters who do not like Trump, a figure that would represent about 11 million registered Republicans nationwide.

Galen said his group will target them between now and November's general election, aiming $50 million at an anti-Trump, pro-Biden persuasion campaign focused on battleground states of Michigan, Pennsylvania, Wisconsin and Arizona.

The digital and TV ad campaign will focus on abortion rights, the blow to US prestige abroad under Trump, and his failure to fully support Ukraine in its war against Russia.

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PrimaryPivot, another pro-Haley group, changed its name to Haley Voters for Biden just after Haley dropped out of the race.

Co-founder Robert Schwartz said the group will target the roughly 500,000 voters who backed Haley in the primary campaign in Michigan and North Carolina, as well as possible Haley voters in Georgia, which holds its primary March 12.

Republican strategist Ford O'Connell, who worked with Trump during the 2020 campaign, said he expected Trump to extend an "olive branch" to Haley supporters but that many were not persuadable.

O'Connell noted that Trump did not go after Haley in his speech on Tuesday night. Trump showed that he "understood that the way to victory is to stay on the issues: the border, prices, foreign policy," O'Connell said.