AMNA NAWAZ: For more on the fallout from the debate for the president and his party, it's time for Politics Monday with Amy Walter of The Cook Political Report With Amy Walter and Tamara Keith of NPR.

Always great to see you both.

Tam, kick us off here.

Now, much of the reporting, much of your reporting, much of ours, showed there's strong concern among Democrats about President Biden's debate performance.

Most of the public statements do not reflect that.

Four days after the debate, where is that conversation?

How real is the panic?

TAMARA KEITH, National Public Radio: Certainly, the public statements have coalesced behind President Biden.

I was talking to the chairman of the -- the Democratic chairman of the state party in Wisconsin today.

And he's closer to the ground.

What he said is, yes, absolutely, the debate was terrible.

His phone was blowing up.

But the people who were most concerned are people who have been paying close attention to the election and watched the State of the Union address, where President Biden did a solid job, or watched some of his speeches where he was on fire, like he was in North Carolina.

He said most voters who aren't paying a lot of attention are pretty much just seeing debate Joe Biden on loop on TikTok leading into this debate.

The guy that they think is running for president, the many voters' believer is running for president is the guy who showed up on the debate stage, somebody who stumbles on the steps and everything that they have seen in loop on TikTok.

AMNA NAWAZ: Amy, what about the impact here?

I mean, do we yet know how much of an impact the debate actually had, both on Democratic voters, who've long had concerns about President Biden's age, but also on Republican or independent voters, many of whom former President Trump still has to try to win over?

AMY WALTER, The Cook Political Report: That's right.

And, Amna, that's a really good point that Democratic voters have been saying now for months and months and months two things.

One, they are -- they do have concerns about his age.

And, two, they wanted to see an alternative to President Biden in the Democratic primary.

And what we're seeing -- and your piece set this up -- is that the very people who could have provided that alternative, whether it was the governors or some of those senators that were in your piece, decided that they didn't want to challenge the president, the sitting president.

And that was the choice that they made.

And that's why we are here now just four months before the election.

There is not going to be a replacement.

That replacement conversation has been happening in periods of time before this, right?

We saw it right before the State of the Union.

We're seeing it now.

It is set.

Unless the president of the United States decides himself that he is stepping down, there is no replacement for him.

The delegates are going to choose him as the nominee.

And the party, this is the choice in front of them.

Now, what are the polls showing post-debate?

We don't have really anything up to date right now because I think we're going to -- it's going to be about a week or so before we see some of the fallout.

I suspect that Trump is going to gain a little bit, based on everything that we have seen for these past four days, because the reality of this election today isn't much different than it was before the debate.

In order for Joe Biden to win this race, for President Biden to be reelected, the election has to be as much about Donald Trump as it is about Joe Biden or even more so about Trump than it is about Biden.

The debate was an opportunity for him to change that focus.

He failed on that measure.

And now it's really all about Biden.

And that is a problem for the Biden campaign.

AMNA NAWAZ: Well, Tam, speaking of former President Trump, we heard William Brangham and Marcia Coyle reporting earlier about the major Supreme Court decision today, essentially saying former President Trump and, by default, then all presidents do have some kind of immunity there entitled to it all, but ends any chance of Mr. Trump facing trial for his federal election subversion case before the November election.

What's your takeaway from that?

TAMARA KEITH: Well, and what I will say is, President Biden is now set to speak about this later tonight.

Certainly, that decision raises the stakes in the election.

That is how the Biden campaign sees it.

And their view -- and they're leaning into it -- as Amy said, this election -- if this election is about Joe Biden, it's a problem for Joe Biden, but if it's about former President Trump, then that is better for the Biden campaign.

And so they are running hard against former President Trump, harder than ever.

And this decision is the latest example.

They say it raises the stakes, because their belief and many voters believe that former President Trump is an existential threat to democracy, and this gives him or any president more power.

AMNA NAWAZ: And we will expect, as you mentioned, President Biden to speak about that a little later tonight.

Amy, what about you?

As you saw that ruling come down, this was highly anticipated, what were your key takeaways?

AMY WALTER: Well, I think that's right, that it was highly anticipated, that this is the ruling that we would see basically, kicking it down to the lower courts.

And essentially, from a practical purpose, what it means is that there will not be any other trials for which Donald Trump will be sitting.

And so that is something that we long suspected, but now is the reality.

And as Tam pointed out, the issue for the Trump campaign is making the case much more firmly that this election is about the economy, is about immigration, it's not about what the Supreme Court or other courts may say in the future.

AMNA NAWAZ: Tam, meanwhile, I know you have been reporting on how former President Trump's campaign has been planning ahead to their party's convention, presenting some kind of a platform later this month.

Tell us what your reporting shows and why it's important.

TAMARA KEITH: Right.

So we have been talking for this whole segment about Democrats in disarray.

And what my reporting shows is that Republicans are further coalescing behind Trump.

The -- his top advisers have a plan to cut back the party platform considerably, to make it shorter, more streamlined, clearer, more concise, and, importantly, very Trump-centric.

It is going to be built around Trump and the ideas that he has pushed forward that helped him win the primary.

And they are trying to avoid drama.

They do not want to put anything in that platform that is going to give their adversaries anything to go after him on.

And so they are going to move the process, which has typically been in front of cameras, behind closed doors, not open press.

This is a break with tradition.

However, it's part of they think they're winning.

They believe they are winning.

They are winning based on the polls.

And they don't want to mess with that by -- with a platform document that's really just a vision document for the party.

AMNA NAWAZ: Amy, weigh in on that from your perspective, I mean, the idea, as Tam's reporting has shown here, that this is the party now further coalescing around him, the platform now further coalescing around former President Trump.

This is a stark contrast to the way things used to be done at the conventions.

What's your take?

AMY WALTER: I know.

I know.

I think that is -- listen, this has been happening for the last few years as we have seen candidates downballot really mold themselves in the image of Donald Trump, looking to get endorsements from Donald Trump.

That is now where the Republican Party is.

And, in fact, I have been thinking about how much where Democrats are right now reminds me of where we were at this point in 2016, when there were questions going into that convention about whether Donald Trump was going to get the elites and the establishment behind him because there were so many concerns about his electability.

But voters were saying, no, this is the person that we want.

And, essentially, the establishment got on board.

In this case, it's the voters on the Democratic side who've been saying for a long time, we'd like an alternative.

The establishment and elites were saying, nope, this is the person that we're sticking with.

And so these conventions are going to look -- are going to be actually quite fascinating to see what the rank and file take from this and what independent or swing voters take away from those two events.

I think it's going to be really, really important.

AMNA NAWAZ: Those conventions now just weeks away.

I know we will all be following them.

AMY WALTER: Yes.

AMNA NAWAZ: Amy Walter and Tamara Keith, always great to see you both.

Thank you so much.

TAMARA KEITH: You're welcome.

AMY WALTER: You're welcome.