Republicans laughed at Trump behind his back after he rambled during a Senate luncheon, according to Mitt Romney's new tell-all book

• Republican Senators laughed at Trump behind his back, Mitt Romney says in his upcoming book. 
• The former President appeared at a GOP Senate luncheon in 2019 days after the Mueller probe concluded. 
• Trump made rambling remarks, and when he left, the senators "burst into laughter," Romney says. 

Mitt Romney's upcoming tell-all book is already revealing what Republican senators really think about Donald Trump.

In one instance they laughed at him behind his back.

Then-President Trump appeared at a 2019 Senate luncheon and he rambled about the Mueller probe coming to a close, according to an excerpt published in the Atlantic from an upcoming biography about Mitt Romney. 

According to the excerpt, Trump made a special appearance at a weekly Senate Repbulicans' caucus lunch in March 2019. He was particularly "buoyant" because his Justice Department had just concluded that Robert Mueller's special investigation didn't prove Trump's 2016 campaign colluded with Russia. 

The Republicans applauded Trump — awarding the former President a "standing ovation" — as he entered. He responded with "rambling remarks" about the long-awaited investigation, the excerpt said. 

Trump talked about the "Russia hoax" and the recent midterms among other topics he swung between, the excerpt said. In the same speech, according to the excerpt, Trump declared that the GOP would soon become "the party of health care."  

The excerpt noted that the senators in attendance listened to what the former President had to say, but as soon as Trump left the luncheon, Romney said, the group of GOP senators "burst into laughter" behind his back. 

Romney's book also calls out other top Republicans like GOP leader Mitch McConnell who allegedly praised Romney privately for calling out Trump.

A McConnell spokesperson said the top GOP senator doesn't remember the conversation.