"I don't have a response," Clinton replied. "If he wins the Republican nomination, we'll have plenty of time to talk about it if Hillary wins."
In recent weeks, Trump has revved up his attacks on both Clintons -- focusing on allegations of sexual assault and sexual misconduct by Bill Clinton.
On Thursday, Trump released a video on Instagram overlaying Hillary Clinton's comments about women's rights on top of tabloid images from the Monica Lewinsky scandal during her husband's presidency.
Bill Clinton has been out on the campaign trail this week on behalf of his wife, first in New Hampshire, and on Thursday in Iowa for the first time.
The "Big Dog" has, however, kept a fairly low profile, delivering restrained speeches that focus heavily on the story of how he met and fell in love with his wife.
But the questions have continued to hound him, despite his insistence that he will not engage.
"I have no interest in getting involved in their politics or doing anything except trying to help Hillary," Clinton added to reporters on Thursday.
Meanwhile, this week, a woman who has accused Clinton of raping her in 1978, Juanita Broaddrick, re-emerged in the spotlight to reiterate those accusations.