AMNA NAWAZ: Welcome to the "News Hour."

It's the eve of the pivotal presidential debate, when Vice President Kamala Harris and former President Donald Trump are set to face off for the first time and possibly the only time between now and November.

GEOFF BENNETT: And with only eight weeks remaining until Election Day, new polling suggests this race is as close as ever.

QUESTION: Are you ready, Madam Vice President?

KAMALA HARRIS, Vice President of the United States (D) and U.S. Presidential Candidate: Ready.

GEOFF BENNETT: Flashing a thumbs-up to reporters on Sunday, Vice President Kamala Harris said she's ready to take on former President Donald Trump, now just one day to go before their first presidential debate in prime time.

The vice president in a radio interview aired this morning sharing what she expects from her opponent tomorrow.

KAMALA HARRIS: We should be prepared for the fact that he is not burdened by telling the truth, and we should be prepared for the fact that he is probably going to speak a lot of untruths.

GEOFF BENNETT: And the stakes are high, with new polling suggesting the race is a dead heat.

The national poll conducted by The New York Times and Siena College shows Trump leading Harris by 1 percentage point, 48 to 47, well within the margin of error.

And among voters who say they still need to learn more about Vice President Harris, 63 percent of them say they don't know enough about her policies and plans.

The vice president, mostly out of sight for the past few days, has been preparing for the debate in Pittsburgh, flying today to Philadelphia, where the debate will be held.

NARRATOR: Now those people have a warning for America.

Trump is not fit to be president again.

GEOFF BENNETT: As her campaign rolls out a new ad featuring clips from former Trump officials, including Mike Pence, warning about a second Trump term.

That's as Donald Trump spent the weekend on the campaign trail, holding a rally in battleground Wisconsin.

DONALD TRUMP, Former President of the United States (R) and Current U.S. Presidential Candidate: We're run by stupid people, stupid, stupid people.

And we found that out at the debate with Joe.

How did that work out?

And we're going to find it out again on Tuesday night.

GEOFF BENNETT: In those same remarks, he promised to pardon January 6 rioters if reelected and on social media this weekend made the baseless assertion that the election will be stolen from him.

And he again promised retribution.

"Those people that cheated will be prosecuted to the fullest extent of the law, which will include long-term prison sentences."

FMR.

REP. LIZ CHENEY (R-WY): A vote for Vice President Harris is the right vote to make this time around.

GEOFF BENNETT: As major voices in the Republican Party, former Congresswoman Liz Cheney and her father, former Vice President Dick Cheney, saying they will vote for Kamala Harris in November, some Trump allies are urging him to stay on message.

FMR.

GOV.

NIKKI HALEY (R-SC): You don't need to go and talk about intelligence or looks or anything else.

Just focus on the policies.

When you call even a Democrat woman dumb, Republican women get their backs up too.

The bottom line is, we win on policies.

Stick to the policies, leave all the other stuff.

That's how he can win.

GEOFF BENNETT: And we will have live special coverage of the ABC News presidential debate.

Tune in tomorrow at 9:00 p.m. Eastern on your PBS station or our YouTube page to watch a simulcast of the debate followed by analysis from our panel of experts.