• Several former state campaign committee members on Nikki Haley's failed presidential campaign endorsed Democratic nominee Kamala Harris over GOP nominee Donald Trump.
• They include former members of Haley's Michigan, Iowa and Vermont campaign teams.
• The former governor and ambassador to the United Nations under Trump was his last high-profile challenger in the 2024 Republican primary but ultimately endorsed him.

Several former state campaign committee members on Nikki Haley's failed presidential bid have endorsed Democratic nominee Kamala Harris, publicly breaking with Haley, who is backing GOP nominee Donald Trump.

"This year the election may well be decided by independents and former Haley supporters," wrote Tom Evslin, who co-chaired Haley's Vermont state leadership team, in an op-ed Wednesday for the Vermont Daily Chronicle.

Evslin, who voted against then-Democratic nominee Hillary Clinton in 2016 and against Trump in 2020, wrote that he "will be happy to vote FOR Harris if she consistently articulates a strong foreign policy."

The same day, two former members of Haley's Michigan state leadership team also urged Republicans to support the Democratic ticket of Harris and Minnesota Gov. Tim Walz.

"As Republicans, we believe character and integrity matter," business consultant Jimmy Greene and communications expert Bill Nowling wrote in a joint op-ed for the Michigan Chronicle. "That's why we proudly supported Ambassador Nikki Haley for president and were part of her Michigan Leadership Team."

Nowling is also a co-chair of the group Republicans for Harris, which includes Republican former Reps. Adam Kinzinger of Illinois and Denver Riggleman of Virginia.

"We believed in her positive vision for the future of the Republican Party, Michigan, and our nation," Greene and Nowling wrote. "Now, we will vote for Vice President Kamala Harris, and we are encouraging other sensible Republicans to join us."

The latest endorsements came five days after Haley's former Iowa state co-chair Dawn Roberts announced she would back Harris.

In a guest column for the Des Moines Register, Roberts wrote that while she is "a lifelong Republican," she was dismayed by both parties when Trump and President Joe Biden appeared to be the top candidates.

When Biden withdrew from the race and endorsed Harris as his replacement, "I decided to see who she really was," wrote Roberts. "I was impressed with how she handled herself saying that she wanted to 'earn everyone's support.' She showed willingness to listen to a wider range of views to solve problems."

"So I am supporting Kamala Harris for president," she wrote.

A spokeswoman for Haley did not immediately respond to CNBC's request for comment on her former campaigners endorsing Harris.

Haley, who was governor of South Carolina and served as U.S. ambassador to the United Nations, was the last high-profile candidate to keep campaigning against Trump in the Republican presidential primary.

In the final stretch of her campaign, Haley, who had taken pains to avoid alienating Trump's base by directly attacking him, became vocally critical of the de facto Republican leader.

When Haley finally ended her campaign in March, she did not immediately endorse Trump, as many other GOP challengers had done. In her concession speech, she said Trump had to "earn the votes of those in our party and beyond it who did not support him."

Haley nevertheless said in May that she would be "voting for Trump."

She later spoke at the Republican National Convention and endorsed Trump more explicitly. In subsequent media appearances, Haley continued to advocate for Trump, even as she clarified that his campaign had not asked her to do so.

Earlier in September, Haley sent a cease-and-desist letter to the political action committee Haley Voters for Harris, Fox News reported.

Haley's primary supporters were viewed as being more moderate and independent than Trump's base. In New Hampshire, which was seen as one of her strongest battlegrounds in the GOP contest, independents make up the largest party affiliation.

"Many of us supported Haley because of her experienced tough foreign policy," Evslin said of the former United Nations ambassador in his op-ed Wednesday.

He urged Harris to take a tougher line on Iran by declaring that the Middle Eastern nation's "worldwide war by proxy will no longer be tolerated."

"Many of us would like to cast a positive vote for Harris. A strong specific foreign policy statement will go a long way to winning our vote," Evslin said.