For years, Hillary Clinton has been asked if she is held to a double standard as a woman in politics. And for years, she has mostly refused to take the bait.

But on Thursday, the day after a top Republican accused her of insufficient smiling at a televised national security forum, Clinton suggested that it was, at least, a question worth considering.

"I'm going to let all of you ponder that last question," she said coyly, holding a news conference in New York with her traveling press corps on an airport tarmac in White Plains. "I think there will be a lot of Ph.D. theses and popular journalism writing on that subject for years to come."

After her appearance at the forum, moderated by NBC's Matt Lauer, Reince Priebus, the chairman of the Republican National Committee, wrote on Twitter that Clinton had appeared "angry + defensive the entire time."

Supporters of Clinton instantly accused Priebus of sexism, and her campaign team moved quickly to amplify the remarks.

On Thursday, Clinton suggested that her demeanor was owed to the "serious issues" being discussed, adding that she did not make a habit of taking advice from the Republican committee. She was not interested, she said, in "just making political happy talk."

"I had a very short window of time in that event last night to convey the seriousness with which I would approach the issues that concern our country," she said, appearing to allude to what critics described as a rushed format.

She noted that Trump had devoted much of his speaking time to praising President Vladimir Putin of Russia.

"Maybe he did it with a smile," she said, now flashing one of her own. "I guess the RNC would have liked that."