AMNA NAWAZ: Well, Senate Democrats won back the majority last week.

Now they're fighting over who will lead it.

Maryland Senator Chris Van Hollen has thrown his hat in the ring and says he spoke with current Democratic Leader Chuck Schumer before officially launching his challenge.

SEN.

CHRIS VAN HOLLEN (D-MD): We understand that this will be a competition.

I think it's important to give Senate Democrats a choice.

That's what we just gave voters all over the country, a choice.

They chose change.

And I think that the Democratic Caucus needs to be open to new ideas, a different way of governing, and a different way of conducting and approaching politics.

AMNA NAWAZ: Our congressional correspondent Lisa Desjardins is here with more on the first serious challenge Schumer has faced to his party leadership.

Lisa, good to see you.

LISA DESJARDINS: Hi.

AMNA NAWAZ: So why does Senator Van Hollen say he's running?

LISA DESJARDINS: First of all, this is a groundswell that has been developing outside of Washington, including from some in the Democratic base, especially progressives, for some time about Schumer.

But Van Hollen says it is about the election results specifically.

He said these new senators who were elected were part of a movement not just about new lawmakers, but about new leaders altogether.

Van Hollen himself is 67 years old.

He's been in Congress since 2003.

But this is by far his most assertive move, going up against Chuck Schumer.

Schumer has been the Democratic leader since President Trump first took office in 2017.

He's a New Yorker.

He knows how to kind of use the strength of leadership.

And timing is everything.

Schumer has been lining up these votes for some time.

And he actually has some ideas that are the same as Van Hollen, including they both want to end funding for the Iran War, perhaps even risking a shutdown.

But Van Hollen is more progressive.

He is someone who's openly saying it's time to end the filibuster.

AMNA NAWAZ: So what are Van Hollen's actual chances here?

Is this a real challenge for Schumer?

LISA DESJARDINS: It is a real challenge, but Schumer, as I'm saying, has a much greater advantage.

And I want to go over exactly why.

The math favors Schumer.

First of all, these are 11 new senators who have so far been elected.

There will be a 12 if Mary Peltola is also confirmed in Alaska.

But take those 11 new senators, the majority of whom oppose Schumer, and compare them with the 44 members of the Senate now who will be voting on this leadership election there in yellow.

You see one of them is Van Hollen, so he has that vote.

But Schumer has been working on this crowd for months getting their votes.

And timing is everything here.

Van Hollen announced relatively late in the game.

So let's look at exactly how many votes each one of them has so far.

You see those opposing Schumer.

There's a number especially of new senators, but he already has locked up all of those commitments.

Schumer has the advantage.

It is notable, of course.

Schumer's the leader right now.

He doesn't have a majority yet publicly pledged to him.

But he says he has the votes.

We will find out in December.

AMNA NAWAZ: We will find out indeed.

Lisa Desjardins, thank you so much.

LISA DESJARDINS: You're welcome.