Ambassador Nikki Haley won a major endorsement from the influential Koch network as she vies to challenge President Trump for the GOP’s 2024 presidential nomination. This comes as Mr. Trump has been taunting his opponents, lording favorable poll numbers over them online.

In a statement Tuesday, the political arm of the Koch fundraising network, Americans for Prosperity, endorsed Ms. Haley in a statement, giving her campaign a significant financial and organizational boost.

“AFP Action is proud to throw our full support behind Nikki Haley, who offers America the opportunity to turn the page on the current political era, to win the Republican primary and defeat Joe Biden next November,” AFP’s president, Emily Seidel, wrote in a memo.

She says Ms. Haley “has what it takes to lead a policy agenda to take on our nation’s biggest challenges and help ensure our country’s best days are ahead.”

“With the grassroots and data capability we bring to bear in this race, no other organization is better equipped to help her do it,” Ms. Seidel concluded.

In the memo, she also criticized Mr. Trump’s influence on the GOP’s political operation, writing that “Republicans have been nominating bad candidates who are going against America’s core principles. And voters are rejecting them.”

The network and Mr. Trump have had a tenuous relationship in the past, with the brothers who headed the Koch network in 2016, Charles and David Koch, refusing to support Mr. Trump’s 2016 campaign, opting instead to support down-ballot Republicans.

Tuesday’s memo made it clear that, even as GOP voters appear to be consolidating behind Mr. Trump in primary polling, the AFP Action Network will be opposing Mr. Trump in the primary.

“In sharp contrast to recent elections that were dominated by the negative baggage of Donald Trump and in which good candidates lost races that should have been won, Nikki Haley, at the top of the ticket, would boost candidates up and down the ballot,” the AFP endorsement reads.

Ms. Seidel also signaled that the group thinks the GOP voter base is ready to move on from Mr. Trump despite what the polling suggests. Ms. Seidel notes that “nearly 75 percent of Republican primary voters say they are open to supporting a candidate other than Donald Trump.”

“In addition, nearly 60 percent of the Republican voters AFP spoke with who have never voted in a primary or caucus say they are ‘extremely enthusiastic’ to vote for the first time,” Ms. Seidel wrote.

However open GOP primary voters are to voting for someone besides Mr. Trump, public polling at this point indicates that nationally, Mr. Trump is still Republican voters’ favorite candidate.

FiveThirtyEight’s average of polls shows that, nationally, Mr. Trump enjoys about 60 percent support, whereas Ms. Haley is at about 10 percent.

The AFP network’s endorsement of Ms. Haley, whom Mr. Trump calls “Birdbrain,” comes as Mr. Trump rails against her and some of his other political opponents and the press online.

“FoxNews should look at these numbers before doing their Fake News reports on Birdbrain. What a joke they are,” Mr. Trump said on Truth Social. “The DeSanctimonious donors are coming to me … not to, ‘I’ll never run against President Trump’ Haley, who was very average in every way.”

Mr. Trump’s post included an image of a Harvard Harris Poll showing him with 67 percent support in the national horse race compared to Governor DeSantis’s 9 percent and Ms. Haley’s 8 percent.

Mr. Trump has also directed his ire toward the governor of Iowa, Kim Reynolds, over her endorsement of Mr. DeSantis in recent days, saying, “Kim Reynolds is now the MOST UNPOPULAR GOVERNOR IN THE NATION.” 

“The great people of Iowa understand loyalty, and don’t like DeSanctimonious, who was against Ethanol and Social Security,” Mr. Trump said.

In his post, Mr. Trump cited a Morning Consult Poll that found that Ms. Reynolds was the least popular governor in America with a 47 percent disapproval rating, up from 39 percent at the beginning of this year.

In the analysis of the pollster, Mr. Trump’s ire may have something to do with a decline in the governor’s popularity: “Her unpopularity increased partly because of a surge in negative sentiment among independent and Republican voters during a year in which she signed a strict anti-abortion law and took a lashing from former President Donald Trump over her apparent closeness with Gov. Ron DeSantis.”