Donald Trump can’t stop saying nasty things about women. It could cost him.

A nasty feud that escalated Thursday between Donald Trump and his chief Republican rival over their wives set off a new wave of alarm among establishment Republicans, who fear that the GOP front-runner would drive away female voters in a general-election fight with likely Democratic nominee Hillary Clinton.

Trump’s gender problem flared again this week as he and Sen. Ted Cruz of Texas traded insults while Cruz’s wife, Heidi, became the target of vitriol on social media from Trump and his supporters. At one point, the real estate mogul retweeted an unflattering image contrasting Heidi Cruz’s appearance with his wife, Melania, a retired model.

Our spouses and our children are off-bounds,” Cruz told reporters while campaigning in Dane, Wis. “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.”

He added: “Donald, you’re a sniveling coward. Leave Heidi the hell alone.”

For months Trump has defended himself against accusations of being offensive to women, saying that he hits all his challengers equally. He labeled former Florida governor Jeb Bush “low energy” and sought to diminish Sen. Marco Rubio of Florida with the nickname “Little Marco.”