DANE, Wis. (AP) — Ted Cruz branded Donald Trump a "sniveling coward" Thursday as the feud between the Republican presidential contenders over their wives took a nastier turn.

After an earlier and vague threat to "spill the beans" about Heidi Cruz, Trump stoked the spat on Twitter when he retweeted side-by-side images of Cruz's wife, with an unflattering grimace, and his wife, Melania, in a gauzy, glamorous pose.

"No need to spill the beans," said the caption. "The images are worth a thousand words."

Ted Cruz, campaigning in Wisconsin, was livid.

"Leave Heidi the hell alone," Cruz said, speaking through reporters to Trump.

"Donald does seem to have an issue with women," he said. "Donald doesn't like strong women. Strong women scare Donald."

Trump was set off this week when a group that opposes him released an ad before the Utah presidential contest raising questions about the propriety of Melania Trump becoming first lady. The ad showed a provocative, decade-old magazine photo of her when she was a model and before she married Trump.

Trump wrongly attributed the ad to the Cruz campaign and warned on Twitter: "Be careful, Lyin' Ted, or I will spill the beans on your wife!"

The lurch into personal territory normally off limits in campaigns came as an anti-Trump super PAC ran an ad in primary states that features women reciting derogatory comments made by the billionaire about women. The ad was produced by Our Principles, a group founded by a former Mitt Romney campaign adviser who is trying to help the Republican Party appeal to more women.

Trump has a substantial lead in the delegate chase for the GOP nomination. Cruz has a stiff challenge trying to catch him in remaining races and may only have a shot at the nomination if the contest spills into the summer convention.