A new book about how President Trump gained his nearly single-handed grip on the Republican Party examines why many of Trump’s sharpest GOP critics changed their tunes, including the former House Speaker Paul Ryan.

A pre-publication copy of the book, “American Carnage,” by Tim Alberta, was obtained by the Washington Post.

Among Alberta’s most striking assertions is that Ryan decided to retire from Congress in January because he saw it as an “escape hatch” to avoid having to work with Trump for another two years. A Ryan spokesperson told The Hill that those are the author’s words, not Ryan’s.

The book includes an interview with Trump himself, who told Alberta the Tea Party is now called “Make America Great Again,” the Post says. “The Republican Party was in big trouble. I brought the party back.”

The book is “filled with vivid details and on-the-record quotes from prominent Republican officials,” the Post says, and “details how many Republicans who once criticized Trump quickly changed their tune after his election, striking a devil’s bargain with a man Alberta describes in the book as behaving in a way that is dishonest, amoral, narcissistic and uninformed.”

Among those featured in the book as Trump opponents-turned-supporters are former White House Press Secretary Sean Spicer; former Trump chief of staff Reince Priebus, and Texas Sen. Ted Cruz.

Alberta aims a particularly sharp jab at Vice President Mike Pence:

Pence’s talent for bootlicking — he was nicknamed ‘the Bobblehead’ by Republicans on Capitol Hill for his solemn nodding routine whenever Trump spoke — were at their most obscene during meetings at the White House,” Alberta writes.

One Democrat in the House saw the Ryan retirement in a different light.