Former GOP presidential candidate Nikki Haley on Monday took issue with ex-Rep. Liz Cheney’s (R-Wyo.) criticism of her offer to campaign with former President Donald Trump to help him secure victory in November.

Cheney, who endorsed Kamala Harris last week and has repeatedly warned Trump poses a threat to U.S. democracy, told ABC’s “This Week” on Sunday that she can’t assess Haley’s decision to embrace Trump “in any kind of a principled way” given her past criticism of the former president during the Republican primary.

In an interview with “Fox & Friends,” Haley said she disagreed with Cheney’s assessment.

“I respect her decision but she can’t say my decision is not principled,” Haley said. “It actually is. We can either vote based on style or we can vote on substance. I’m voting based on substance.”

Haley also claimed Trump’s policies on several issues, including the economy, immigration and foreign policy, are better for the country compared with the current administration’s record, which she pinned exclusively on Harris.

“We should be very clear. If you don’t like him, say you don’t like him,” Haley said of Trump. “But you can’t say that his policies are worse than Kamala Harris’. That’s just not a fact.”

Haley conceded the upcoming election will be tightly fought and, once again, said she would be willing to appear with Trump on the campaign trail if he wanted.

“I’m on standby,” she said. “I’m happy to be helpful. I don’t want to see Kamala Harris win. He’s the candidate. He can decide whether he needs my support or not.”

Haley, who withdrew from the Republican presidential primary in March, had repeatedly described him as unfit to serve another term in the White House, calling him “unstable and unhinged.”

While she did not immediately endorse Trump after dropping out of the race, she eventually said in May that she would vote for him and spoke in support of his White House bid at the Republican National Convention in July.

Haley also previously served in Trump’s administration as United Nations ambassador.

Cheney and her father, former Vice President Dick Cheney, publicly announced their support for Harris last week.

“As citizens, we each have a duty to put country above partisanship to defend our Constitution,” Dick Cheney wrote in a statement.

Still, many Republicans on Capitol Hill dismissed the elder Cheney’s unprecedented move as irrelevant.

“I think he’s out of touch,” Sen. Cynthia Lummis (R-Wyo.) said.