GEOFF BENNETT: Welcome to the "NewsHour."

Nikki Haley's bid for the White House is now over.

AMNA NAWAZ: The former South Carolina governor suspended her campaign today, setting up a rematch between President Biden and former President Trump.

Speaking in Charleston this morning, Haley did not promise to back her party's likely nominee.

NIKKI HALEY (R), Presidential Candidate: It is now up to Donald Trump to earn the votes of those in our party and beyond it who did not support him.

And I hope he does that.

At its best, politics is about bringing people into your cause, not turning them away.

And our conservative cause badly needs more people.

This is now his time for choosing.

AMNA NAWAZ: To discuss what comes next in the race for the White House, I'm joined now by Republican strategist Kevin Madden, who's worked on Mitt Romney's presidential bids.

Kevin, good to see you again.

KEVIN MADDEN, Republican Strategist: Good to be with you.

AMNA NAWAZ: So let's just start with Haley's announcement today.

What do you make of that announcement on this day after what happened yesterday on Super Tuesday?

KEVIN MADDEN: Well, I think the numbers and the math became very obvious and that Nikki Haley realized and her campaign realized that she just didn't have a path to the nomination.

I think it's pretty startling if you look at Trump's numbers and how dominant he was in this Republican presidential primary, 64 percent of the overall vote, 24 contests versus Nikki Haley, who won two contests, and 90 percent of the delegates.

This -- there is a voice for Nikki Haley and Nikki Haley-like candidates, I think, inside the party, but it is very clear right now that this is a Donald Trump party driven and fueled by a MAGA base.

And the Haley campaign came to that realization, based on the numbers they saw yesterday.

AMNA NAWAZ: So, in that same vein, we today saw outgoing Senate Minority Leader Mitch McConnell endorse Mr. Trump officially, despite past criticism of him, especially after the January 6 insurrection.

Here's a part of what Mr. McConnell said.

SEN. MITCH MCCONNELL (R-KY): I said in February of 2021, shortly after the attack on the Capitol, that I would support President Trump if he were the nominee of our party, and he obviously is going to be the nominee of our party.

AMNA NAWAZ: So, Kevin, Haley has not endorsed Mr. Trump.

Do you think she will?

KEVIN MADDEN: I think she will ultimately.

But it is going to be an endorsement that is going to feel like an extraction over a long period of time.

I think, clearly, first of all, the open wounds of a presidential primary will take some time to heal.

But I think, if she's looking to still have a voice in the party and still play a role in the direction of the party, that ultimately playing a role in unifying that party, which has its divisions, would be probably in her best political interests.

AMNA NAWAZ: So, where do her supporters go?

I mean, you take a look at the delegate count.

She did have a number of people backing her, although her delegate count did not compare to Mr. Trump's.

She ended up with 89 delegates to his 1,031.

Where does the more than $12 million she raised in February go?

Where do her backers go?

KEVIN MADDEN: Well, I think backers, as well as voters, they are not a monolithic bloc for Nikki Haley.

She has made an incredible, I think, impression on a lot of Republican voters, but she's not yet a movement candidate.

So, I don't think that these voters are sort of calcified around Nikki Haley and waiting for a signal from Nikki Haley.

I think they're very much up for grabs.

They're up for grabs for Donald Trump.

He's going to have to work hard to gain their support and win them back in November, especially if he wants to win.

But some of them are up for grabs as well for President Joe Biden.

So, the Nikki Haley voter, the profile of the Nikki Haley voter is the profile of a swing voter in a lot of key battleground states.

They're going to determine who wins or loses this election.

AMNA NAWAZ: Does former President Trump need them, though?

Because to hear him today and his online post in response to yesterday, it doesn't look like he's courting them exactly.

This is what he had to say.

He said: "Nikki Haley got trounced last night.

Much of her money came from radical left Democrats, as did many of her voters, according to the polls.

At this point, I hope she stays in the race and fights it out until the end."

It's not exactly an appeal to Haley voters.

KEVIN MADDEN: Yes.

And, look, first of all, if we remember 2020 election, it came down to about 300,000 voters across six states.

So, all of these votes count.

So, you're going to try and get as many voters -- of these Haley voters as possible if you want to win, Right?

But if today was the starter pistol for the general election and you looked at how Donald Trump tried to appeal to these swing voters and how Joe Biden tried to appeal to them by saying, hey, he's going to try and earn their vote, he wants to be a uniting force for Republicans, Democrats, and independents, you have to give the edge to Biden on starting to the race towards winning these voters over.

AMNA NAWAZ: When you look at where the party is now and the fact that Mr. Trump is now the presumptive nominee, you see he beat out more than a dozen challengers.

Nikki Haley also beat out most of them as well.

She did it as a woman, as a woman of color, made history in her race, was beating President Biden in some hypothetical matchups.

But the party said, we're going with Trump.

We're going with the guy who lost to Biden, who's facing all these criminal charges, who was twice-impeached.

What does this say to you about the voters and where the party is right now?

KEVIN MADDEN: Right.

Well, a lot of those general election polls that showed Nikki Haley winning, they weren't necessarily a reflection of a primary electorate, right?

So the primary electorates are much less interested in bringing people together and finding common ground.

Primary electorates are much more interested in trying to find a candidate that's going to fight the perceived opposition the other side.

And that, I think, is why Donald Trump won this primary so resoundingly, which is that he spoke to those voters and said he's going to be a fighter for them.

So I think it tells you that Donald Trump has a very, very firm grip on this party, yet he has not done the work needed yet to really build out and appeal to the broader, big middle of the American electorate.

That big middle of the American electorate that's caught between what I would describe as like the 47-yard lines of American politics, they're going to decide who wins or loses this election.

AMNA NAWAZ: Got eight months to go.

Kevin Madden, thank you so much.

Always great to talk to you.

KEVIN MADDEN: Great to be with you, as always.