Former “Celebrity Apprentice” contestant and Fox News personality Geraldo Rivera said Monday that he is endorsing Vice President Kamala Harris for president over his longtime friend, former President Donald Trump.

In a lengthy social media post, Rivera called Trump “a sore loser who cannot be trusted to honor the Constitution. This is why I am voting for Kamala Harris to be our 47th President.”

After placing second on the last season of the Trump reality competition series in 2015, Rivera said he viewed Trump as “a loyal friend” who allowed him regular access to the White House while president.

“My resulting coverage gave him the benefit of most doubts,” he wrote on social media. “His presidency was underrated.”

Rivera said he stuck by Trump during special counsel Robert Mueller investigation into Russian interference in the 2016 election, and said he had been personally reassured by Trump in a phone call following his loss in the 2020 election that he would do the right thing if a recounting of the vote showed he had lost.

“It never did,” Rivera said. “Instead, President Trump embarked on an increasingly menacing campaign to discredit the 2020 election. With a motley supporting cast of increasingly fringe characters, he careened from one bizarre theory to the next, offering no meaningful proof, that he had been robbed by the Democrats.”

There is no evidence of widespread voter fraud in the 2020 presidential election, a statement backed up by officials in both parties. Claims of voter fraud brought by Trump and his allies were rejected from courts nationwide, including the U.S. Supreme Court.

Rivera charged that Republicans who believe Trump’s false claims of a stolen election are liars themselves: “He has coaxed and intimidated tens of millions into pretending he was reelected in 2020, and that the election was stolen.”

Writing directly to Trump supporters, Rivera said it’s “better to admit he lost last time but that you don’t care because a Harris presidency would be a disaster, or you admire his defiance in the face of an assassin’s bullet. Just don’t pretend that he got robbed in 2020. That is a lie.”

Rivera left Fox News last year after 23 years with the network, citing “growing tension that goes beyond editorial differences and personal annoyances and gripes.” The network characterized the exit as amicable.