According to a recently-released book by Mark Leibovich, a staff writer at The Atlantic, former Republican Sen. Alan Simpson blasted the current iteration of the GOP as a "cult."

The 90-year-old ex-Wyoming lawmaker was deeply critical of what he deemed "the tragedy of what has occurred" during the tenure of "this vicious animal who has poisoned"

Simpson, who served in the Senate from 1979 to 1997 and voted for Trump in the 2016 presidential election, said he wouldn't back the former commander-in-chief again if he ran for president again in four years.

He criticized the state of the party for being driven by the "Make America Great Again" movement.

Simpson said in the book that his party no longer talks about common sense or politics.

He said that this is no longer a Republican Party. A cult is what it is.

The former senator spoke with a prominent GOP figure about what he felt was the decline of the party.

Simpson appeared in a campaign ad for Liz Cheney, who has become one of the biggest Republican critics of Trump's election claims.

Cheney was first elected to the House in 2016 and quickly rose up the leadership ladder by becoming the House Republican Conference Chair in 2019).

A series of hearings have brought previously undisclosed revelations about the events of that day to the public, as a result of her work as the vice chair of the January 6 committee investigating the Capitol riot.

In Wyoming, where Trump won 70% of the vote in the 2020 election, Cheney's outspokenness quickly led to multiple GOP challengers trying to oust her in the party primary.

A recent poll shows the congresswoman trailing her opponent by 22 percentage points.

Simpson went after the former president when he spoke with NBC News last month.

He said that the congresswoman's efforts on the January 6 panel were obvious to many Americans.

He said that the guy is so full of himself that he would overturn the rule of law because of his own ego.

Simpson was awarded the Presidential medal of freedom by his Senate colleague Biden during a White House ceremony.