Doubling down on his comments on women, Donald Trump engaged in war of words on Twitter Friday with Hillary Clinton, setting up a bigger battle than the first presidential debate.

In the overnight hours, Trump continued his tirade against Miss Universe Alicia Machado, tweeting, "Did Crooked Hillary help disgusting (check out sex tape and past) Alicia M become a U.S. Citizen so she could use her in the debate?"

Clinton responded, "This is ... unhinged, even for Trump," adding, "What kind of man stays up all night to smear a woman with lies and conspiracy theories?"

"I think the man is coming unraveled," said Massachusetts Senator Elizabeth Warren.

Sen. Warren, who's become a vocal Trump opponent, said Friday that these Twitter rants show that Trump lacks the discipline to be president.

"I don't understand how you base a presidential campaign saying you want to run to be president of all people by attacking people all across this country," said Sen. Warren.

Trump's one-on-one Thursday with necn's Alison King made national news as he addressed his threat in Monday's debate to say "something extremely rough" about Clinton, possibly concerning Bill Clinton's infidelity.

"I would have been able to do it if I wanted to do it, I didn't want to do anything like that in front of Chelsea, their daughter, who I happen to think is a very nice young woman," Trump told King.

King asked, "Why would that reflect on Hillary Clinton anyway?"

"You'll have to figure that out," he replied. "I think it's very simple to figure that out."

Senator Warren said this was Trump showing his true colors.

"This is like the jet fuel for his campaign are attacks on other human beings," said Sen. Warren, "and I think it's time for the American people to just say no."