The birther issue is an issue because Donald Trump is letting it be an issue. And despite his supporters' best efforts to argue that it's not an issue, Trump isn't cooperating. He still hasn't said President Obama was born in the United States, no matter what Rudy Giuliani says.

Much like Giuliani and the others, Trump supporter and former congressman Jack Kingston (R-Ga.) tried to argue Friday night on MSNBC's "Hardball" that this was much ado about nothing.

Donald Trump now says Obama was born in the U.S. – but falsely blames Clinton for starting rumor (Peter Stevenson/The Washington Post)

And NBC's Katy Tur was having none of it. In a tense exchange with Kingston, she explained to him exactly why this issue hasn't been laid to rest.

"Donald Trump has not backed away from this because he's never backed away from any statement on this campaign trail so far," Tur said, stopping Kingston from interjecting. "The only thing we've heard him back away from was to say that he regrets some of the things he said during this campaign season, but he never specifically said what he regretted."

She added: "The issue is, whenever anybody has asked him this, he has refused to back down from it. I understand that you may say, Mr. Kingston, that the polling doesn’t agree with me, but I’m going to tell you, as somebody who’s been doing this now for 14 straight months -- I think we’re going on 15 months now -- and that is the same conversation I’ve had with supporter after supporter in city after city in this country. Doesn't matter if we’re in the South, in the West, in the East, the North. Every city I’ve been to, there have been people who’ve said exactly those words."

Below is the transcript:

TUR: Let me address something that Mr. Kingston was saying, that it was not an issue of this campaign. Donald Trump may not be making it an issue on the campaign trail, on the stump, but I have to tell you, his supporters believe it’s an issue.

When you ask them about President Obama -- not just a handful, not just a few, many of them say...

KINGSTON: That does not show up in the polls!

TUR: ... that they believe he was born in Kenya. Hold on. I’m telling you I’m there every day on the campaign trail. I talk to supporters every single day.

KINGSTON: But that doesn’t show up on any poll!

(CROSSTALK)

KINGSTON: ... that say that to people.

TUR: Please don’t interrupt me, sir. Please don’t interrupt me, sir.

KINGSTON: I mean, he can...

(CROSSTALK)

TUR: Let me tell you what Donald Trump supporters tell me on the campaign trail...

(CROSSTALK)

MATTHEWS: Let Katy report here. Let Katy report here.

TUR: Let me tell you what Donald Trump supporters tell me on the campaign trail often. They often say that they believe that Donald Trump (sic) was born in Kenya. They often say that they believe he’s a Muslim. Some of them even go on to say that they believe he’s an undercover operative, a Manchurian candidate, if you will, that has the interests of a foreign power...

KINGSTON: OK, Katy...

(CROSSTALK)

TUR: ... the American public. That being said, Donald Trump has not backed away from this. And let me finish this, Mr. Kingston. Donald Trump has not backed away from this because he’s never backed away from any statement on this campaign trail so far.

The only thing we’ve heard him back away from was to say that he regrets some of the things he said during this campaign season, but he never specifically said what he regretted. We’ve asked him repeatedly, as Chris just showed -- I asked him last year -- where he stands on the birther movement right now. He was asked as late as last week on his own press plane by the press pool. He said he doesn’t want to get into it because he believes it’s going to become an issue.

The reality is, it’s become an issue regardless of it. I spoke to a senior aide...

KINGSTON: Katy...

TUR: ... who said that if he was asked about it again...

KINGSTON: Just a minute. Just a minute.

MATTHEWS: Let her finish.

TUR: ... that if he would -- if he would asked about it again, then he come out and say that he does not believe that Donald Trump (sic) was born overseas, that he believes he was born in Hawaii. The issue is, whenever anybody has asked him this, he has refused to back down from it.

I understand that you may say, Mr. Kingston, that the polling doesn’t agree with me, but I’m going to tell you, as somebody who’s been doing this now for 14 straight months -- I think we’re going on 15 months now -- and that is the same conversation I’ve had with supporter after supporter in city after city in this country. Doesn’t matter if we’re in the South, in the West, in the East, the North. Every city I’ve been to, there have been people who’ve said exactly those words.

KINGSTON: And you want me to believe people come up to you unsolicited, unprodded, and say the reason why I support...

TUR: Yes!

KINGSTON: Katy, come on. Let’s...

TUR: You don’t have to believe me. I’m telling you the facts of what happens in the field.