Former Vice President Mike Pence said Friday he will not be endorsing his former boss and two-time running mate in the 2024 general election, a nod to the deep divisions between the two men that has formed since they left office.

“It should come as no surprise that I will not be endorsing Donald Trump this year,” Pence, who ran an unsuccessful 2024 presidential campaign of his own, said on Fox News.

“Look, I’m incredibly proud of the record of our administration. It was a conservative record that made America more prosperous, more secure, and saw conservatives appointed to our courts in a more peaceful world,” Pence said. “But that being said, during my presidential campaign i made clear there were profound differences between me and President Trump on a range of issues.”

Trump is the presumptive Republican nominee for November’s election, setting up a rematch with President Biden.

Pence has for roughly two years been outspoken that he did not have the authority to reject the 2020 election results on Jan. 6, 2021, despite a pressure campaign from Trump to do so. In launching his own campaign, Pence argued Trump’s actions on Jan. 6 were disqualifying.

The former vice president told Fox News that his differences with Trump go beyond that day, citing the former president’s lack of a plan to confront the national debt, his evasive comments about restrictions on abortion and his recent opposition to a ban on TikTok, something their administration pursued in 2020.

“In each of these cases Donald Trump is pursuing and articulating an agenda that is at odds with the conservative agenda that we governed on during our four years,” Pence said. “And that’s why I cannot in good conscience endorse Donald Trump in this campaign.”

Pence was an unflinchingly loyal vice president for Trump throughout their time in the White House, but he emerged as one of the former president’s most outspoken critics during his own 2024 GOP primary campaign, which ended last October.

The former vice president frequently warned the party against following what he called the “siren song” of populism and questioned whether Trump was committed to conservative policy goals.

Pence joins former New Jersey Gov. Chris Christie (R) and former Ambassador to the United Nations Nikki Haley as ex-challengers to Trump for the nomination who have yet to endorse him.

Others who ran against Trump, including Sen. Tim Scott (R-S.C.), Florida Gov. Ron DeSantis (R), North Dakota Gov. Doug Burgum (R) and entrepreneur Vivek Ramaswamy (R), have all endorsed the former president.

Pence’s advocacy group announced last month it would spend $20 million to shape the conservative agenda and help elect conservative candidates.