As the Democratic presidential candidates took to the sidewalks of New York, the tenor of the campaign was approaching the gutter -- with each side raising questions about the other's qualifications for the highest office in the land.

Senator Bernie Sanders defended some of his recent comments about Hillary Clinton in an interview with "CBS This Morning" anchor Charlie Rose.

CHARLIE ROSE: You said that Secretary Clinton doesn't qualify because she takes super PAC money and has supported trade deals.

BERNIE SANDERS: What I said was in response to what she has been saying. Washington Post headline, quote, "Clinton questions whether Sanders is qualified to be president." I thought it was appropriate to respond.

ROSE: But is it tit for tat? Is that what this campaign conversation ought to be about?

SANDERS: No, it certainly should not be. And as you may know, I have tried to run an issue-oriented campaign which is what I believe the American people wanna hear. They want to hear about what ideas we have to improve their lives, not just attacking each other every day. 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.

ROSE: Do you believe Secretary Clinton is unqualified to be president?

SANDERS: Well, does Secretary Clinton believe that I am unqualified to be president?

ROSE: But why can't you simply say yes? She has a first-rate resume in terms of a life in public service. She's one of the most qualified people to run.

SANDERS: She has years of experience. She is extremely intelligent. You know, I have some experience too. I have a pretty good record in Congress, as a senator, as a mayor. I think I am qualified to be president. And so to answer your question, you're right. We should not get into this tit for tat. We should be debating the issues facing the American people. All I am saying, if the people are gonna attack us, if they're gonna distort our record, as has been the case time and time again, we're gonna respond.

ROSE: People are saying the tenor of this campaign has changed, and it's sounding more and more like the Republican campaign.

SANDERS: Let's not go that far.

ROSE: But take a listen to this, this is what you've said. You said that, "Clinton should apologize for Iraq war deaths."

SANDERS: This is after I was asked to apologize for the tragedy in Sandy Hook. You know, put these things into context.

ROSE: Tit for tat.

SANDERS: It is tit for tat. But I'm responding to attacks that are being made against me.

ROSE: I'm asking where the tenor of this campaign is going. And is that going too far to say she bears responsibility for Iraqi war deaths?

SANDERS: Do I bear responsibility for the tragedy and the horrors of Sandy Hook? So, you know, let's get off of that. Of course she doesn't bear responsibility. She voted for the war in Iraq. That was a very bad vote, in my view. Do I hold her accountable? No.

ROSE: Do I hear you saying tonight that, "I'm embarrassed by these personal attacks that are taking place. And all I have done is respond to attacks. But I'm embarrassed, and they are giving a tone to this campaign that I don't like. I don't like the fact that I have to participate in it and I wish it would stop on both sides." Are you willing to say that?

SANDERS: Yup. Oh yeah. Look, Charlie, you're looking at a guy who's been in politics for a long time. Ran many elections in the state of Vermont. I have never run a negative ad in my life. In this campaign, as I'm sure you can appreciate, every other day people are coming up to me and saying "Aren't you gonna attack Hillary Clinton? Aren't you gonna attack the Clinton Foundation?" And you know how many times I've done that? Zero. You saw me in the debate, right?

ROSE: Yes.

SANDERS: Well, I was asked about emails. What did I say? I said, "Enough of these damn emails."

ROSE: I just wanna come back to the Iraqi thing one second, and one more question. You have said that she voted for the Iraqi war. Other people did as well. Many other people. Do you hold all of them responsible for the deaths of Americans?

SANDERS: No.

ROSE: Then why say it, Senator? That's the question.

SANDERS: I am saying it because I was attacked.

ROSE: That's not a reason, I promise you, to say, "I'm saying it because they attacked me."

SANDERS: Well, I hope you ask Senator Clinton am I responsible -- look, you know, I'm being asked to apologize -- you know--

ROSE: Come November 2016, if Hillary Clinton is the nominee you will be supporting her?

SANDERS: Sure, I will. Look, as I said a million times, 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. And if Secretary Clinton is the nominee, I will certainly support her.

Watch more of Charlie Rose's interview with Sanders Thursday night on "Charlie Rose" and on Friday's "CBS This Morning."