The stage is set for what could be the pivotal moment in the campaign leading up to the November 5 U.S. presidential election – Tuesday night’s debate between Democratic Vice President Kamala Harris and Republican former President Donald Trump.

The two candidates have never met each other or even talked on the phone, but on Tuesday they will be standing a short distance from each other behind lecterns at the National Constitution Center in Philadelphia. They are set to trade barbs with each other for 90 minutes while answering questions posed by two ABC News anchors, David Muir and Linsey Davis.

Harris, Trump to debate Tuesday in pivotal moment of campaign

Tens of millions of Americans are likely to watch the encounter between the two presidential candidates in what could be the only debate of the campaign. The event takes place eight weeks before the official Election Day but only days ahead of when early voting starts in some of the country’s 50 states.

Harris, Trump to debate Tuesday in pivotal moment of campaign

National polling shows the contest to be close, making it all the more crucial for both candidates to make their best case in the debate for the small number of voters who haven’t already made up their mind. At stake, returning Trump to the White House after he lost reelection in 2020 to President Joe Biden or elevating Harris, Biden’s second-in-command.

Harris, Trump to debate Tuesday in pivotal moment of campaign

When Biden dropped his reelection bid in July after a stumbling debate against Trump in late June and endorsed Harris as his successor, Democrats quickly coalesced around her candidacy. While Biden trailed Trump when he ended his campaign, Harris has edged ahead of Trump in numerous national polls by two or three percentage points.

A -Siena College poll released Sunday showed Trump with a 48-47% lead nationally even as the newspaper showed Harris ahead in an average of multiple polls in three crucial battleground states, Wisconsin, Michigan and Pennsylvania, with the two candidates tied in four other crucial states, Arizona, Georgia, Nevada and North Carolina.

The seven highly contested states are expected to play an outsized role in determining the outcome of the election because the U.S. does not pick its president and vice president by the national popular vote.

Rather, the election is 50 state-by-state contests, with electors for the winning ticket in all but two states casting all their votes in the Electoral College for either Harris and her vice presidential running mate, Minnesota Governor Tim Walz, or Trump and his ticket mate, Ohio Senator JD Vance. Electoral College votes are based on population, so the most populous states hold the most sway.

The new -Siena poll showed that the debate stakes are particularly high for Harris in introducing herself to the American public, with 28% of those surveyed saying they need to know more about her, while only 9% said the same about Trump.

University of Michigan debate coach Aaron Kall told VOA, “Tuesday night is one of the most highly anticipated and consequential presidential debates of all time. Trump is a seasoned presidential debater but has a history of making controversial remarks against opponents on stage, which could distract from a more important focus on substantive policy issues.”

“Harris just entered the race in July and is still being defined by voters and the Trump campaign. She must demonstrate she can prosecute the case against Trump's first term in office and recent actions,” he said. “Trump is an especially effective counter puncher and could employ a scorched earth debate strategy if he feels unfairly maligned on stage.”

Kall added, “Both candidates should stress their compelling biographies and unique skill sets that make them especially qualified to lead the country during the next four years.”

He said the two candidates “must get these voters to feel comfortable with the notion of them being president for the next four years and a regular fixture on their television screens and in their living rooms.”

Harris has been preparing for the debate at a Pittsburgh hotel in the crucial battleground state of Pennsylvania. She has held several mock debates with a Trump-like substitute, complete with television lighting and would-be moderators asking her pointed questions.

Trump has engaged in policy briefings with his aides, shunning mock debates with a Harris-like figure.

On the debate stage, the rules for Harris and Trump will be the same as in June. Each candidate’s microphone will be muted when the other is speaking. Each will have two minutes to answer a moderator’s question and the other a minute to respond.

Abortion rights, immigration at the U.S. border with Mexico, crime rates in the United States and personal character are among the issues that the ABC anchors are likely to raise.