Harris and Trump face off in highly anticipated ABC debate

President Obama was fond of saying, “Elections have consequences.” He could have said the same about presidential debates.

That sentiment has rarely been more evident than today, 51 days after President Biden's unclear and weak debate performance against former President Trump helped prevent the incumbent from seeking a second term.

Trump and Vice President Kamala Harris will meet for the first and possibly only time at 6 p.m. PDT on Tuesday in a debate that could once again change the course of what has been an extremely close election campaign.

The 90-minute debate at the National Constitution Center in Philadelphia appears to have even more at stake than in previous elections in the television era, in which candidates generally agreed to at least two, and often three, debates in the general election.

The showdown will be broadcast by ABC News and several other networks and moderated by ABC anchors David Muir and Linsey Davis.

Whether the past is just a prologue and what the past actually means will enliven the competition.

Read more:Debate night is here: What to expect when you've learned to expect the worst

Harris, 59, is expected to portray Trump's four years in office as a time of unrest, division (especially toward immigrants) and restrictions on personal freedoms – especially a woman's once constitutionally protected right to abortion.

Trump, 78, argued that his four years in office were a happy time for America, when both unemployment and inflation were low and there were no foreign wars that drained billions of dollars from the United States.

When assessing the era from 2021 to today, when Biden and Harris occupied the White House, the tide will turn.

Trump will portray the last four years as a time of chaos and uncertainty, with inflation skyrocketing during the Democrats' early years and illegal border crossings at the U.S.-Mexico border soaring.

The Republican candidate is expected to echo a line made by his predecessor, Ronald Reagan. In the second of two debates with President Carter, just a week before Election Day in 1980, Reagan stood in front of the camera and asked Americans if they were “better off” than they had been four years earlier.

Her supporters expect Harris to take a challenging approach: on the one hand, she will praise the successes of the past four years and, on the other, suggest that as president she will be better able to respond to two issues that are of utmost importance to many voters: economic hardship and immigration.

To make that argument, the vice president will almost certainly look to Democrats' initiatives to lower drug prices, especially insulin, and other budget-saving measures, such as student loan forgiveness.

Trump and his advisers have tried to blame Harris for all of Biden's failures, even going so far as to claim that the vice president is the shadow power running the Democratic administration. Harris will likely respond that she was present at important discussions but was not the one making the final decisions.

If Trump were to take forceful action in this direction, the Vice President could respond: Was Vice President Mike Pence the real power in the White House under Trump?

Among the many differences between the candidates is the way they prepared for the debate. Harris has been settling into Pittsburgh since late last week and preparing formally, with simulated questions and answers.

Democratic activist Philippe Reines, a longtime aide to Hillary Clinton, portrayed Trump during the election campaign.

“We should be prepared for the fact that he doesn't care about telling the truth,” Harris said in a radio interview on the “Rickey Smiley Morning Show.” “He's fighting for himself, not for the American people, and I think that will come out as the debate progresses.”

Read more:Meet the Harris-Trump debate moderators: ABC News' David Muir and Linsey Davis

In an interview with his friend, Fox News host Sean Hannity, Trump said he had no particular strategy and would “get a feel for it as the debate progresses.” Trump quoted former heavyweight champion Mike Tyson: “Everyone has a plan until they get punched in the face.”

True to form, Trump complained that he was not being treated fairly by ABC anchors, denigrating the network and suggesting it was a tool of the Democratic Party. Before the June 27 debate with Biden, he launched a similar preemptive strike, denouncing CNN as “fake news” and anchors Jake Tapper and Dana Bash as biased.

But after Biden's stumble, Trump's advisers decided to focus on the incumbent, saying CNN and its anchors had been fair. It was Biden's team that complained – saying Bash and Tapper should have called the former president out for his many lies.

Trump's falsehoods in the June debate included his unproven claim that Biden ordered the prosecution against him and his claim – refuted in several polls – that the American people want Roe v. Wade to be overturned so that states can determine their abortion policies.

CNN's anchors left it almost entirely up to the candidates to expose each other's falsehoods in June. No one knows whether ABC's Muir and Davis will step in or let the vice president and former president conduct their own search for truth.

The Associated Press contributed to this report.

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This story originally appeared in the Los Angeles Times.