GWEN IFILL: It has been a months-long waiting game, but now that we know Vice President Biden will not make another run for the White House, what drove his decision, and what does it mean for the rest of the 2016 field?

Glenn Thrush, the chief political correspondent for Politico, has been covering this, and in many ways was able to see around the corner in this magazine profile earlier this year, "Joe Biden in Winter."

Glenn joins me now.

So, after all the ups and the downs and the speculation, no go. Why?

GLENN THRUSH, Politico: No, I mean, there is a number of reasons, sort of bifurcated between his emotional life and this terrible tragedy that he suffered with the death of his 46-year-old son, Beau, in May, but also there was really no political path.

Biden is sort of a political procrastinator. He's a very improvisational politician and he really waited too long. Hillary Clinton's performance in the first debate and this commensurate rise in the polls that she saw afterwards simply left him with no path.

GWEN IFILL: Your story that you posted this afternoon, you quote someone as saying that all the meetings, all the speculation, all the ways they were running traps was more fantasy football than football.

GLENN THRUSH: Yes, I think he was really confined to a relatively small group of advisers. Shouldn't surprise folks who know the way that Biden operates, a lot of his family.

His son Hunter, his remaining son, was really pushing him for this. Also, Mike Donilon, a longtime aide from Delaware, was pushing this. But the rest of the family was fairly ambivalent and his larger circle of advisers were more facilitating what he wanted to do, but I think many of them over time came to believe that he ultimately wouldn't go for it.

GWEN IFILL: Another thing that you wrote in your earlier piece, it talked about one of his friends and advisers saying that in his career Joe Biden had climbed almost all the way to the top, and then someone moved the ladder.

GLENN THRUSH: Can you imagine what that must feel like?

GWEN IFILL: Yes.

GLENN THRUSH: This is a guy who has done everything — quote, unquote — "right."

The problem is, at some point, he reached, I think, his own ceiling. The 1988 presidential campaign, which was disastrous for him, he was accused of plagiarizing Neil Kinnock's speeches, a U.K. politician.

GWEN IFILL: Yes.

GLENN THRUSH: Really, I think that was his moment. In 2008, he ran a very bad presidential campaign. I think Biden is really an example of, when a politician has a moment and they cannot capitalize on that moment, the rest of their career really is a postscript.

GWEN IFILL: What was the significance of doing this in the Rose Garden with not only his wife, but President Obama by his side?

GLENN THRUSH: Well, the initial significance for those of us who were still wondering what was happening, we knew then he was going to say no. He wasn't going to say yes standing next to the president.

But I think the significance is that Joe Biden views himself as both a family man, as symbolized by his wife — getting Jill on board was one of the big challenges for this. And he never really quite closed the deal with his own wife.

But the more important point here is, he views himself very much as a partner with President Obama, and that relationship, which really had its ups an downs in the first term, has really deepened into something more personal. I have been told…

GWEN IFILL: He went out of his way today to embrace that legacy.

GLENN THRUSH: Yes. And apparently after this, they embraced in the Oval Office. It was sort of a tearful moment.

And the president, I am told, has been very, very concerned about Biden's state of mind subsequent to Beau Biden's death. This is something that really weighs on everyone.

GWEN IFILL: So he said today the window had closed.

Was it Hillary Clinton basically who closed the window?

GLENN THRUSH: I think she sort of slammed it on his fingers.

If Hillary Clinton had performed badly in that first debate or there had been more damaging revelations about the e-mails that had come out, I think we might be dealing with a different fact set. But my sense is that really did it.

GWEN IFILL: And she went out of her way, we can take a look, to be very gracious in her response to him.

She said, among other things: "Joe Biden is a good man and a great vice president. I'm confident that history isn't finished with Joe Biden. As he said today, there is more work to do, and if I know Joe, he will always be on the front lines, always fighting for all of us."

Now, let's just talk polls. With Joe Biden out of the race, Hillary Clinton can afford to be as gracious as she is.

GLENN THRUSH: Oh, absolutely.

I think it is a good day. I'm sure she had a nice cup of tea and watched this thing several times. Look, in all of the polls that we have seen, Biden takes away from Hillary Clinton's support in battleground states and nationally as well. So what this means is that I think it's quite likely we are going to see a bump in the national polls and in New Hampshire and in Iowa for Hillary Clinton.

GWEN IFILL: No Bernie Sanders bump out of this? None of the people who are supporting Bernie Sanders were drawing toward Biden?

GLENN THRUSH: Yes, Biden is a fairly centrist — you could make the argument Joe Biden, in the longer span of his career, has actually been more conservative than Hillary Clinton on a lot of things.

He has tacked to the left, as everyone in the Democratic Party has recently, but Biden's affiliation is with the white working-class voters. And Bernie Sanders much more appeals to the sort of coastal elites. I think Sanders will see a little bit of a bump, because I'm sure some supporters will flock to him. But I think Hillary Clinton is the one who is going to be the predominant recipient.

GWEN IFILL: And, finally, the vice president seemed to signal today this is not the end of his career. He still wants to be heard.

Is there any history of a second-term vice president who is not running for president being heard after finally withdrawing?

GLENN THRUSH: I think you make a very good point here. I think his moment of maximum leverage has passed.

I think the one thing that is left is an endorsement. As we know — and I covered Hillary Clinton in 2007 and 2008 — there are a lot of bumps left in this road, and she will need to pull some endorsements out of her pocket during times of need. I think the final card that he has to play is an endorsement.

GWEN IFILL: Well, we will be all waiting for that, that it will have a huge impact, perhaps, perhaps not.

That's the thing we like about campaigns, Glenn Thrush of Politico. Thank you very much.

GLENN THRUSH: Great being here.