President Trump escalated his criticism of Paul Ryan, accusing the former House speaker of nearly killing the Republican Party.

Trump's tweets Saturday are the latest in a growing conflict that began last week when excerpts from an upcoming book emerged that showed the Wisconsin Republican left Congress because of his disdain for the commander in chief.

"House Minority Leader Kevin McCarthy is a far superior leader than was Lame Duck Speaker Paul Ryan. Tougher, smarter and a far better fundraiser, Kevin is already closing in on 44 Million Dollars. Paul’s final year numbers were, according to Breitbart, 'abysmal,'" Trump said. "People like Paul Ryan almost killed the Republican Party. Weak, ineffective & stupid are not exactly the qualities that Republicans, or the CITIZENS of our Country, were looking for. Right now our spirit is at an all time high, far better than the Radical Left Dems. You’ll see next year!"

This followed a salvo of tweets late Thursday in which Trump took shots at Ryan over his ill-fated run as Mitt Romney's running mate in the 2012 presidential election and record as a congressman.

"Paul Ryan, the failed V.P. candidate & former Speaker of the House, whose record of achievement was atrocious (except during my first two years as President), ultimately became a long running lame duck failure, leaving his Party in the lurch both as a fundraiser & leader," Trump said in the first of three tweets.

"When Mitt chose Paul I told people that’s the end of that Presidential run. He quit Congress because he didn’t know how to Win. They gave me standing O’s in the Great State of Wisconsin, & booed him off the stage. He promised me the Wall, & failed (happening anyway!)," Trump continued. "He had the Majority & blew it away with his poor leadership and bad timing. Never knew how to go after the Dems like they go after us. Couldn’t get him out of Congress fast enough!"

Romney, now a senator for Utah, came to Ryan's defense on Friday.

"The fault for our 2012 loss is mine alone; @SpeakerRyan was a tireless campaigner, fundraiser, and conservative champion. As the sole person who could unite the House, he acquiesced to be Speaker as a service to the country," Romney said. "His selfless leadership and lifelong policy work were critical to the tax and regulatory reform that have helped propel the economy," a follow-up tweet reads. "A man like Paul Ryan does not often come along."

Ryan ended his 20-year tenure as a U.S. congressman in January when the Democrats took over as the majority party in the House. The upcoming book, "American Carnage" by Tim Alberta, says Ryan saw retirement as an "escape hatch" in not dealing with Trump anymore.

"We’ve gotten so numbed by it all,” Ryan says in the book. "Not in government, but where we live our lives, we have a responsibility to try and rebuild. Don’t call a woman a ‘horse face.’ Don’t cheat on your wife. Don’t cheat on anything. Be a good person. Set a good example."

"I told myself I gotta have a relationship with this guy to help him get his mind right," Ryan added. "Because, I’m telling you, he didn’t know anything about government ... I wanted to scold him all the time."

Ryan said he and others worked hard to stop Trump from "making bad decisions. All the time."

Trump and Ryan have shared a shaky dynamic. Ryan cut ties with then-candidate Trump when the Access Hollywood tape emerged in October 2016. Even though Republicans had control of both the House and Senate for Trump's first two years in office, legislation for some of Trump's biggest priority platforms, including funding for a border wall across the U.S.-Mexico, failed to make it to his desk.

In an interview with the Daily Caller in January, Trump accused Ryan of reneging on a deal to fund the wall made in exchange for a 2018 omnibus spending bill.

But Trump had nothing but praise for Ryan when the Wisconsin Republican announced he was not going to run for reelection in 2018. "Speaker Paul Ryan is a truly good man, and while he will not be seeking re-election, he will leave a legacy of achievement that nobody can question. We are with you Paul!" Trump tweeted in April 2018.

Republicans lost control of the House because of a disastrous 2018 midterm election in which Democrats flipped 40 seats in the lower chamber.

In "American Carnage," Trump called Ryan a "f---ing Boy Scout."