Ted Cruz warned Donald Trump not to "attack women" Thursday after the Republican frontrunner appeared to escalate the personal feud over their wives.
"Donald, real men don't attack women," the Texas senator wrote after the billionaire retweeted an unflattering photo of Heidi Cruz.
The exchange came after Trump showed no sign of backing down in the dispute over a campaign ad that featured an old picture of Melania Trump posing handcuffed and nude for GQ magazine.
The flare-up prompted Jeb Bush to endorse Cruz Wednesday in a rebuke to what the former Florida governor called the "divisiveness and vulgarity" of Trump.
Trump repeated late Wednesday that he believed Cruz "knew about" the ad, which appeared to be aimed at persuading Mormon women to support Cruz in Tuesday's Utah primary.
The ad was created by the anti-Trump Make America Awesome Again super PAC and featured a photo shoot of Melania from 2000 with the meme caption: "meet Melania Trump. Your next first lady. Or, you could support Ted Cruz on Tuesday."
As polls closed in Tuesday's contests, Trump tweeted : "Lyin' Ted Cruz just used a picture of Melania from a G.Q. shoot in his ad. Be careful, Lyin' Ted, or I will spill the beans on your wife!"
On Wednesday, Cruz told NBC's TODAY that Trump's threat "speaks volumes about character" and "is the epitome of classlessness."
"If Donald is trying to mess with my wife, he's way out of his league," he added
Asked by Fox Business host Lou Dobbs if he was going to raise the standard of a campaign that had become "so unseemly," Trump responded: "I agree with you … I mean … I wrote and said, 'Be careful because otherwise I'll have to start talking about your situation.' Now, do I like doing that? No. Should that have been done by him? He knew absolutely about it … He knew about it."
Trump said Melania was "very smart" and "would be a great first lady," adding that the edition of GQ featuring her on the cover was a "very successful issue."
He added: "Ted Cruz knowingly … I mean, he said he didn't know, but that's again why I call him 'lying Ted' … Ted Cruz knowingly, in my opinion, had this article sent all over Utah."
He then retweeted a supporter who posted an image in which Heidi Cruz was compared unflatteringly to Melania, with the meme caption: "No need to spill the beans. The images are worth a thousand words."
Cruz responded early Thursday: "Donald, real men don't attack women. Your wife is lovely, and Heidi is the love of my life."
Separately, Cruz pledged an intense campaign in New York, two months after deriding Trump for having "New York values." The Cruz campaign believes it can also pull off a victory in neighboring New Jersey, a winner-take-all state with 51 delegates on the line.
This story originally appeared on NBCNews.com.