What's at stake with Harris and Trump set to face off on debate stage

It's an historic night that could shape the course of the presidential election that is now just 55 days away.

A new PBS News / NPR/Marist poll shows that 70 percent of Americans say they will be tuning in tonight , while another quarter plan on following at least some coverage.

Nearly a third say the matchup could influence their pick for the top of the ticket.

Lisa Desjardins : This is essentially a contest to try and define Kamala Harris in the eyes of swing voters.

She says she expects the showman to show up tonight , and she's been preparing for that.

The vice president spent roughly five days or so in Pittsburgh , Pennsylvania , before heading to Philadelphia yesterday , only briefly stepping out to visit local businesses.

Lisa Ling: Harris may try to differentiate herself from Biden on the economy by showing a bit more empathy on inflation and affordability.

She says she will try to goad President Trump on election denial specifically, speaking potentially directly to him, saying that he lost and trying to get him to admit he lost.

The Trump campaign is trying to focus on crime and immigration, taking Ameshia Cross' point that this is an election that's going to be decided at the margins.