John Boehner is not a big fan of Ted Cruz.
So much so, in fact, that the former Republican House Speaker told an audience at Stanford University Wednesday that the Texas senator is "Lucifer in the flesh" and a "miserable son of a bitch."
Asked about the 2016 presidential candidate at a forum hosted by Stanford in Government (SIG) and the Stanford Speakers Bureau, Boehner drew laughter for making a face of disgust, according to The Stanford Daily.
"Lucifer in the flesh," Boehner said, according to the paper. "I have Democrat friends and Republican friends. I get along with almost everyone, but I have never worked with a more miserable son of a bitch in my life."
He added that he would vote for Donald Trump in a general election if he becomes the Republican nominee but that he would not vote for Cruz. Boehner was reportedly urged by the event's moderator, Professor David M. Kennedy, to be frank because the event was not being broadcast.
Cruz responded to Boehner first on Twitter and then while addressing media ahead of a rally in Indiana by linking the former congressman to Trump and calling the comments proof that the GOP frontrunner is the favorite among Washington insiders.
"If you're happy with John Boehner as speaker of the House and you want a president like John Boehner, Donald Trump is your man," Cruz said.
"I've never worked with John Boehner," Cruz continued. "Truth of the matter is I don't know the man...If I had said 50 words to John Boehner in my life, I would be surprised."
The former Ohio lawmaker had kinder words for his "texting buddy" Donald Trump, with whom Boehner has played golf with for "years."
And he described another 2016 candidate, John Kasich, as a "friend" too, although he suggested that the relationship takes "more effort" than others.
"[Kasich] requires more effort on my behalf than all my other friends … but he's still my friend, and I love him," Boehner said.
Cruz famously led a group of hard-line conservatives who derailed House leaders' attempts to avoid a government shutdown in 2013. Cruz's failed attempt to force the defunding of President Barack Obama's signature health care law resulted in a 16-day shutdown that was widely seen as politically damaging for the Republican Party.
The senator said Thursday that Boehner declined to meet with Cruz and Utah Sen. Mike Lee during the 2013 shutdown after the two reached out to him about figuring out a potential solution.
Boehner stepped down from his role as House Speaker last September under political pressure from conservatives on Capitol Hill.
When asked about his former colleague's comments, House Speaker Paul Ryan said he has "a much better relationship than that with Senator Cruz" and that it's his job to "unify" the party.
"I have a very good relationship with both of these men, and I intend to keep it that way," he added.
This story first appeared on NBCNews.com. This story has been updated.