AMNA NAWAZ: A milestone moment in the U.S. Senate today, the 300th tiebreaking vote, and an even bigger moment in history for Vice President Kamala Harris, who has now broken 33 deadlocks, more than any other V.P.

before her.

Lisa Desjardins takes a look at Harris' role in a polarized Senate.

LISA DESJARDINS: On watch next to the Senate chamber sit the busts of vice presidents past, some famous, some infamous, many now forgotten.

But none ever saw what just happened, a 191-year-old record broken.

KAMALA HARRIS, Vice President of the United States: On this vote, the yeas are 50 and the nays are 50.

LISA DESJARDINS: Vice President Kamala Harris first tied and now clinched the record for most tie votes cast by any vice president.

SEN. CHUCK SCHUMER (D-NY): The record Vice President Harris sets today is significant, not just because of the number, but because of what she's made possible with tiebreaking votes.

LISA DESJARDINS: Her tiebreaking votes have included some especially weighty ones.

KAMALA HARRIS: The Senate being equally divided.

LISA DESJARDINS: The nearly $2 trillion American Rescue Plan with COVID stimulus.

KAMALA HARRIS: The vice president votes in the affirmative.

LISA DESJARDINS: Last year's Inflation Reduction Act with climate and health care provisions and over a dozen... KAMALA HARRIS: The vice president votes in the affirmative, and the nomination is confirmed.

LISA DESJARDINS: ... nominees from the Federal Reserve to federal courts.

KAMALA HARRIS: The vice president votes in the affirmative.

KELLIE CARTER JACKSON, Wellesley College: It shows that there's a lot of power that Kamala Harris has in her role right now in deciding really the direction of the country.

LISA DESJARDINS: Kellie Carter Jackson is a historian and professor at Wellesley College.

She points out that Harris is always already historic, the first female vice president, the first Asian American, and the first African American.

And she has now taken the record for the most ties from John C. Calhoun, perhaps the most influential white supremacist in U.S. history.

He argued slavery was good for Black people.

KAMALA HARRIS: Do you solemnly swear that you will support and defend... LISA DESJARDINS: It's unlikely he ever imagined someone like Harris in the Senate... KAMALA HARRIS: The nays are 50.

LISA DESJARDINS: ... much less casting its deciding vote.

KELLIE CARTER JACKSON: Occupying those spaces of a Black woman or woman of color, I think it is unprecedented.

But I also think that what's interesting is that when you compare her leadership alongside someone like John C. Calhoun, the two couldn't be further apart.

LISA DESJARDINS: And consider this.

It took Calhoun nearly eight years to rack up 31 tiebreaking votes, but Harris beat that number in just over two.

FMR.

LT. GOV.

BILL BOLLING (R-VA): I think it just reflects the political polarization that exists in the broader society.

LISA DESJARDINS: Bill Bolling is a professor of policy and government at George Mason University and: FMR.

LT. GOV.

BILL BOLLING: So, I have the distinction of having cast more tiebreaking votes than any lieutenant governor in the history of our state.

LISA DESJARDINS: In the 2000s, the Virginia Senate, like the U.S. Senate today, was narrowly split, and sometimes evenly so.

As lieutenant governor, Bolling cast dozens of tiebreaking votes.

FMR.

LT. GOV.

BILL BOLLING: Well, it's a lot of responsibility.

LISA DESJARDINS: And burden.

When the Senate is in town, Harris must be also.

Her supporters say this is one reason her approval ratings aren't higher.

She can't travel and build a profile as easily.

WOMAN: So now they might need the veep?

LISA DESJARDINS: But also, in these tie votes, whether state or national, are broader lessons.

FMR.

LT. GOV.

BILL BOLLING: As a political scientist, I'm often reminding my students that we are living in one of the most political -- politically polarized times in American history.

And that's going to increase the frequency with which these tiebreaking votes occur.

And it's going to increase both the responsibility, but also the power and the influence that these presiding officers can provide.

LISA DESJARDINS: Joe Biden never cast a single tie vote as vice president.

But Harris told CBS her repeated job of it is a bonding point.

KAMALA HARRIS: In fact, the president and I joke.

And when I leave one of our meetings to go break a tie, he says, "Well, that's going to be a winning vote."

Whenever I vote, we win.

It's a joke we have.

But the stakes are so high.

LISA DESJARDINS: High stakes in an institution where process is power and where no vice president has ever been as decisive of a vote as this one, with more tiebreaks almost certainly ahead.

For the "PBS NewsHour," I'm Lisa Desjardins.