Republican presidential frontrunner Donald J. Trump lobbed a low blow at Sen. Ted Cruz's wife Wednesday night following uproar over an attack ad aimed at Trump's own wife, Melania, which featured her sprawled naked on a fur rug. 

A manual retweet on Trump's Twitter feed featured a picture of Trump's wife, a former supermodel, next to an unflattering picture of Heidi Cruz, the wife of the Texas senator running against Trump. "A picture is worth a thousand words," the tweet read.

Cruz responded with a tweet that attempted to take the high road, saying that Trump's wife is "lovely" and that Heidi Cruz "is the love of my life."

Earlier on Wednesday, Trump threatened to "spill the beans" on Heidi Cruz — evidently because he thought the Cruz campaign was behind an incendiary ad released ahead of the Utah caucuses that showed a naked picture of his wife with the phrase: "Meet Melania Trump. Your next first lady. Or, you could support Ted Cruz on Tuesday." 

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Here was Trump's response to the ad:

The ad, paid for by the Make America Awesome super PAC, is not explicitly associated with the Cruz campaign — a point Cruz made on Twitter, adding that the threat against his wife by the business mogul was cowardly. 

"#classless," Cruz, who won with nearly 70 percent of the vote in Utah on Tuesday, wrote in the tweet.