Charles Koch's anti-Trump group endorses Nikki Haley in Republican primary

Americans for Prosperity Action, an advocacy organization backed by billionaire Charles Koch and his network of wealthy conservatives, on Tuesday morning endorsed Nikki Haley as the Republican alternative to Donald Trump ahead of the Iowa caucus that begins the 2024 primary in less than 50 days.

A memo circulated by the the Americans for Prosperity CEO, Emily Seidel, described Haley, a former U.N. ambassador and former governor of South Carolina, as offering "America the opportunity to turn the page on the current political era."

Seidel told reporters later on Tuesday that "Haley has what it takes to lead a policy agenda that will take on our nation's biggest challenges and help ensure our country's best days are ahead of us. And with the grassroots and data capability that we bring to bear in this race no other organization is better equipped to help her do it."

A senior adviser to AFP Action, Michael Palmer, said Haley's policies largely align with the group's free market ideology and "while we don't agree with any person on every issue, Haley offers the best opportunity to improve the lives of all Americans.”

In a statement, Haley said she was "honored" to have the group's backing. "AFP Action’s members know that there is too much at stake in this election to sit on the sidelines," she said, adding, "We have a country to save, and I’m grateful to have AFP Action by our side."

The Koch-backed group stayed out of the 2016 and 2020 presidential cycles but has significant resources to try and boost Haley's campaign, though AFP Action is so far staying mum on how much it plans to spend. The group reported raising more than $70 million in its last public filing, in June, with $25 million coming from Koch himself and another $25 million from one of his nonprofit groups.

The group first announced plans to oppose Trump back in February, based in large part on concerns about his ability to defeat President Joe Biden. Since then, however, the Republican base has only embraced Trump more.

He now leads his closest primary rival in national polls, Florida Gov. Ron DeSantis, by nearly 50 points in 538's average. Haley narrowly trails DeSantis in the national average.

But the situation in early-voting states is slightly different and Trump is a relatively weaker front-runner there, even though he still leads the field by double digits.

DeSantis, Haley and former New Jersey Gov. Chris Christie are hoping an upset in Iowa, New Hampshire or South Carolina could prove they are a viable option for primary voters across the country, though their campaigns so far this year have yet to notably weaken Trump's standing.

AFP Action thinks it can make a difference: ABC News reviewed several internal memos, based on the organization's polling and door-knocking operations in early states, suggesting that about four in 10 GOP voters in Iowa and New Hampshire say the primary campaign "hasn't begun" or has "just started."

AFP Action also believes that three in four Republicans are open to a Trump alternative if they think that person has a better chance of winning.

Following their endorsement on Tuesday, AFP Action plans to pivot from their identification efforts of waffling Trump voters to persuasion against him, focusing their efforts and organizations and advertising on their chosen candidate. They released a new ad spot on Tuesday simultaneously with their endorsement.

They also plan to mobilize large-scale events and push turnout.

DeSantis' campaign sought to play down the AFP Action endorsement of Haley, with spokesman Andrew Romeo attacking her in a statement as a "moderate who has no mathematical pathway of defeating the former president."

"No one has a stronger record of beating the establishment than Ron DeSantis, and this time will be no different," Romeo said.

The Trump campaign said in its own statement that AFP Action was part of an "America Last movement" but that the "swamp creatures in Washington will stop the MAGA movement or President Trump from being the Republican nominee and defeating Crooked Joe Biden."

The endorsement of Haley comes at a potentially significant point in the 2024 race.

Nobody has ever had leads as big as Trump's in the primary and then failed to go on to win their party's nomination, and the winners in Iowa and New Hampshire have a checkered track record. But Trump's campaign is also grappling with his slew of unprecedented legal troubles, all of which he denies, which will complicate his calendar with court appearances and trial dates.

Seidel, the CEO of Americans for Prosperity, said that "early in the cycle, Americans were clear: 70% didn't want Trump or Biden to run."

The group's endorsement is intended to "ensure this opportunity isn't squandered."

ABC News' Abby Cruz, Hannah Demissie, Lalee Ibssa, Jonathan Karl, Nicholas Kerr, Soo Rin Kim, Rick Klein, Will McDuffie and Kendall Ross contributed to this report.