AMNA NAWAZ: All right, let's turn back now to the Republican campaign and the first day of the party's convention right here in Milwaukee.

GEOFF BENNETT: And our Politics Monday team is here with us.

That's Amy Walter of The Cook Political Report With Amy Walter and Tamara Keith of NPR.

And we should say that the house band is back on stage.

(LAUGHTER) AMY WALTER, The Cook Political Report: I know.

GEOFF BENNETT: Delegates are taking to the floor.

We could have some background music for this conversation.

AMY WALTER: Yes.

AMNA NAWAZ: There we go.

On that note, Amy, kick us off here.

The big news of the day, obviously, the selection of J.D.

Vance as former President Trump's running mate.

AMY WALTER: That's right.

AMNA NAWAZ: What do you make about it?

What does he bring to the ticket?

AMY WALTER: Yes, I mean, I think when the Biden campaign made clear the other week that they believed that the easiest path for them to win the Electoral College was through the blue wall, I think picking J.D.

Vance in that -- by picking J.D.

Vance, I think the Trump campaign is saying, OK, you want to fight for the blue wall?

We will pick a blue wall candidate, somebody who grew up in poverty in Ohio, somebody who could have an appeal with his populist message to those voters in that area of the country, try to win over some of those voters.

He did not pick someone, though, who was going to try to appeal maybe to suburban women, right?

This was really very much leaning in on the MAGA message.

And he is essentially saying that, with the pick of Vance, that the sort of MAGA movement is exactly what he wants to campaign on for this next four years.

He's not going to suddenly shift to become more of a sort of traditional Republican in the pre-Trump era.

GEOFF BENNETT: And, Tam, you have got to imagine the Biden team is getting their opposition research together, if they haven't already, I mean, just the reams of things that J.D.

Vance had said about Donald Trump years ago and the memo -- or the -- rather, the statement that Amna mentioned from Jen O'Malley Dillon where she said, the reason Donald Trump picked J.D.

Vance is because J.D.

Vance will do the things that Mike Pence wouldn't.

TAMARA KEITH, National Public Radio: Yes, and that is very much the line that they are delivering from the Biden campaign.

Vance is also someone who has taken positions on abortion that the Biden campaign believes they can make hay with.

He has said things about rape and incest and exceptions that most voters would find offensive.

And they are going to make sure that those statements are repeated and repeated and repeated.

As President Trump, former President Trump has tried to soften the Republican image on abortion, move away from some of the more hard-line views, Vance, before he became the running mate, said things that he's now having to calibrate.

AMNA NAWAZ: What does -- Tam, what does this ticket now say to you in terms of the messaging moving forward, especially in light of where we are?

After that assassination attempt, even Donald Trump was saying, we have to have unity moving forward.

And then he picks the guy who was perhaps most aggressive in terms of blaming Democrats directly for that attack.

Do you expect that kind of unity message to continue even here this week?

TAMARA KEITH: Right.

Just to go back to the tweet that J.D.

Vance put out in the hours immediately after the assassination attempt, he said that President Biden's rhetoric led directly to President Trump's attempted assassination.

He drew a line that does not appear to exist.

And the Biden campaign has said, as Laura said, that they are not going to shy away from making the democracy arguments.

The president was pressed by Lester Holt.

And he said, well, I didn't say he was in the sights.

I said in the bullseye, and that just means I wanted to talk about issues.

But the fact that Biden is being asked about that is a testament to the fact that that line of thought has been elevated by J.D.

Vance and others.

I don't know what's going to happen in terms of the tone and the rhetoric.

AMNA NAWAZ: Thank you.

TAMARA KEITH: I think everyone is talking about bringing the temperature down.

Let's see how low the temperature stays today, tomorrow, the next days.

AMY WALTER: That's right.

TAMARA KEITH: And the Biden campaign has also said that Biden's going to be out there campaigning tomorrow and reiterating a message that he delivered on Friday that very much went after Trump on policy, but went after Trump as an existential threat.

That theme of the campaign on both sides is not going away.

GEOFF BENNETT: What about his age?

In this election cycle, where you have majorities of voters saying that both candidates are too old... AMY WALTER: Yes.

Yes.

GEOFF BENNETT: ... in J.D.

Vance, you have someone who will turn 40 years old in August.

AMY WALTER: Yes.

GEOFF BENNETT: And this notion that, oh, he's too young, he's untested, well, Barack Obama blew that out of the water when he ran and when he won.

AMY WALTER: I know, exactly.

I think what they were also looking for is this contrast with the age argument.

And it's the argument that the Trump campaign has been making from the very beginning.

He's strength.

Biden is weakness.

By having a fighter on his ticket like J.D.

Vance has been, that only adds to that message.

I think the other thing about Vance, given that he was such a critic of Trump in the 2016 campaign, it's a reminder to everyone out there, especially every Republican, that, you know what?

I have made a lot of converts.

I have changed this party from what it was to what it is.

You're either -- and you're on the team or you're not on the team But J.D.

Vance is an example, I think, of somebody who he was able -- he can make the case that, I brought converts in with this message that is resonating.

TAMARA KEITH: Yes.

And what I would say is that this is the Trump campaign doubling down on its theory of the case... AMY WALTER: That's right.

TAMARA KEITH: ... which is not that they are going to go sway a bunch of undecided women in the suburbs, but that they are going to find MAGA voters who just aren't voters yet.

They are going all in on finding and building that base, rather than expanding the tent.

AMNA NAWAZ: On the Democratic side, Amy, as Laura was reporting earlier, the entire conversation around changing... AMY WALTER: I know.

AMNA NAWAZ: ... the Democratic ticket in this new post-assassination attempt, is that now over with?

AMY WALTER: It sure feels like, and people that I was talking with and texting with this weekend, it sure felt like, if it's not completely over, the odds are very, very, very low.

It really took all the winds out of the sails.

And let's face it.

We have known this from the very beginning.

If Joe Biden is digging in, if the president says, I'm staying around, there is nothing that the Democrats can do to make a change on the top of the ticket.

GEOFF BENNETT: So, bottom line, what I hear you both say in different ways is that Donald Trump selecting J.D.

Vance as his vice presidential pick is a sign that he's feeling pretty good about where he stands in this race right now.

TAMARA KEITH: Yes.

And he does feel pretty good.

But just as the Trump campaign plan is to expand -- just build the base, go with the base, the Biden plan is not that.

Their plan is to do a battle of inches for every single undecided and ambivalent voter out there.

And so I think that we're seeing that Biden has dug in.

He doesn't seem to be going anywhere.

And it's not clear that they can push him.

I will say, I did go out door-knocking with some Democratic volunteers over the weekend before the assassination attempt.

And none of the voters whose doors got knocked on brought up the idea of Biden getting out.

Instead, though, they were basically like a pox on both their houses.

I can't believe these are the choices we have, is what voters were saying.

AMNA NAWAZ: It feels like a message we have been hearing for a while now.

AMY WALTER: For a long time.

GEOFF BENNETT: Yes.

AMNA NAWAZ: That's right.

Tamara Keith, Amy Walter, always great to see you both.

Thank you so much for being here.

TAMARA KEITH: You're welcome.