DANE, Wis. — Donald Trump’s ability to roil the presidential race with a few swipes of a smartphone was revealed again in Wisconsin. Before a visit to a factory, Sen. Ted Cruz (R-Tex.) — the only Republican currently stumping here — had to field questions about the week’s second late-night Trump tweet that mocked the senator’s wife, Heidi.

“Our spouses and our children are off bounds,” Cruz said. “It is not acceptable for a big, loud New York bully to attack my wife. It is not acceptable for him to make insults, to send nasty tweets — and I don’t know what he does late at night, but he tends to do these at about 11:30 at night, I assume when his fear is at the highest point.”

The source of Cruz’s ire seemed, as has become Trump’s habit, petty and puerile. Trump, who has no public appearances scheduled until a March 29 rally in nearby Janesville, was angered by a Web ad from the tiny Make America Awesome PAC, allegedly targeted at Mormon voters, that displayed a salacious photo of the mogul’s wife, Melania, from a magazine shoot and warned that she could become first lady unless Utahans caucused for Cruz.

Here are six times Republican presidential contender Donald Trump has insulted women, from Rosie O'Donnell to Ted Cruz's wife, Heidi. (Sarah Parnass and Nicki DeMarco/The Washington Post)

The PAC has no relationship to Cruz, but on Tuesday night, Trump warned that he would “spill the beans” about Heidi Cruz; on Wednesday night he retweeted someone who compared an unflattering photo of Mrs. Cruz to a glamorous one of Mrs. Trump.

In Dane, where Cruz had come to tell blue-collar workers about his economic plan, he seemed physically repulsed by having to respond to this.

“Heidi,” the senator said, before looking down and pausing for several seconds. “She is the daughter of Christian missionaries. She lived in Africa as a little girl. She is an unbelievable mom. We’ve got two little girls, 7 and 5, Caroline and Catherine. They’re going to join us on the road, and I tell you, I’m not looking forward to telling the girls why Donald Trump is launching insults and attacks at their mother. It is not acceptable. Real men don’t bully women.”

He tried to move on, discussing the size of his Utah victory (and not mentioning his defeat in Arizona), but was asked if it was getting “harder to respect” Trump.

“It’s not easy to tick me off,” Cruz said. “I don’t get angry often. But you mess with my wife, you mess with my kids, that’ll do it every time. Donald, you’re a sniveling coward. Leave Heidi the hell alone.”

Cruz’s daughters, in fact, have been the rare human beings immune from Trump’s insults. But Cruz’s tone echoed the one he revealed when Washington Post cartoonist Ann Telnaes published a caricature of his daughters as monkeys dancing at the instruction of their organ-grinder father. The Post took down the online animated cartoon.

Now, as then, Cruz zoomed around a follow-up question about whether he could ever support Trump as a Republican nominee.

“I’m going to beat him for the nomination,” he said. “Donald Trump will not be the nominee. The reason why Republicans are coming together and uniting is that Donald Trump is a train wreck.”

Republican presidential candidate Ted Cruz is blasting rival Donald Trump for a National Enquirer story accusing Cruz of having five mistresses. Here's a breakdown of how a week of fighting got us here. (Sarah Parnass/The Washington Post)