Fox News host Geraldo Rivera once again called out President Donald Trump for how he has handled the results of the election.

Rivera has often sided with Trump and his supporters when it comes to policy but has recently soured on the president, whose legal team has failed to find concrete evidence of election fraud.

On Saturday, Rivera compared Trump to an "entitled frat boy" for not conceding the election.

In response, Trump loyalists attacked Rivera, a mainstay on Fox News since 2001.

Ahead of Election Day, Rivera had publicly expressed his support for Trump. He explained how his “friend” wants the best for America, and though they may have some differing opinions, still wanted Trump to get re-elected.

Amid Trump's initial talk of voter fraud, Rivera had sided with the president through tight voter counts in a few key swing states.

Later, Rivera reversed his position when it became clear that there was no path to victory. He said it was time for Trump to “move on with grace and dignity.”

Trump has remained adamant about not conceding the election. Many Republican lawmakers have confirmed that Democrat Joe Biden won the election.

Biden received more than 7 million more votes than Trump and won the electoral vote, 306-232.

News anchor Geraldo Rivera attends the annual Charity Day hosted by Cantor Fitzgerald and BGC at Cantor Fitzgerald on Sept. 11, 2015, in New York City. Noam Galai/Getty Images for Cantor Fitzgerald