During an interview on CBS News, host Charlie Rose quizzed Sen. Bernie Sanders (I-VT) on his recent remark that Hillary Clinton is not “qualified” to be president, asking the senator whether the tone of the Democratic primary has changed.

Sanders told Rose that he he was simply responding to Clinton and a headline in the Washington Post that said Clinton “questioned” whether Sanders was qualified, a defense Sanders used earlier in the say at a press conference.

“But is it tit for tat? Is that what this campaign conversation ought to be about?” Rose asked.

“No, it certainly should not be,” Sanders said in response. “But what I do have to say, Charlie, if we are getting attacked every single day by the Clinton campaign, I want them to know we’re gonna respond in kind.”

When asked by Rose if he believes Clinton is qualified, Sanders asked in response, “Well, does Secretary Clinton believe that I am unqualified to be president?”

“But why can’t you simply say yes? She has a first-rate resume in terms of a life in public service,” Rose pressed.

Sanders agreed that Clinton has a lot of experience but again said that when he’s attacked, he will respond.

“People are saying the tenor of this campaign has changed, and it’s sounding more and more like the Republican campaign,” Rose said.

“Let’s not go that far,” Sanders hit back.

After grilling Sanders on his comment that Clinton should apologize for deaths in the Iraq war, Rose asked Sanders if he will support Clinton in the general election if she wins the nomination.

“I think the idea of a Donald Trump or a Ted Cruz presidency would be an unmitigated disaster for this country. I will do everything in my power and work as hard as I can to make sure that that does not happen,” Sanders replied. “And if Secretary Clinton is the nominee, I will certainly support her.”

Watch the interview via CBS: