The rerun of the 2020 U.S. presidential election campaign is set for its first high-stakes clash on Thursday, when Joe Biden and Donald Trump, the president and defeated president, go head to head in a 90-minute debate in Atlanta, Georgia.

No audience, prepare to be muted

The impact of TV debates on voters has been hotly discussed since the first featuring party candidates in 1960, when both Biden and Trump were in their teens, but Pew Research does suggest voters find the debates useful, if not necessarily determinative. Pew conducted post-election surveys from 1988 to 2016, and in most cases six-in-10 or more voters said the debates were very or somewhat helpful in deciding which candidate to vote for.

This year, the campaigns have agreed to go about things a little differently. The recommendations of the Commission on Presidential Debates have been jettisoned, and Trump has agreed to sign up to two debates and a tough series of rules which appear to benefit Biden, on by far the earliest date any such debate has ever been staged – and before either man has been officially nominated by their parties.

Thursday’s debate, organized by CNN and moderated by the network’s Jake Tapper and Dana Bash, will begin at 9 p.m. EST. There will be no studio audience, two commercial breaks, each candidate’s microphone will be muted while the other is speaking, and no props will be permitted. Each man will be armed with a pen, a notepad and a bottle of water.

Presidential debates continue to attract high live viewership in the digital age. More than 73 million people watched at least some of the first Biden-Trump clash in 2020, according to Nielsen Media Research. And in a time when digital campaigning dominates and every interaction is filmed, clipped and posted online, a good soundbite is no longer just about making the evening news – those clips will be pushed, pulled and shared around the world and back.

Targeting undecideds

While many voters have already made up their minds ahead of the November 5 election, expected to again be decided by thin majorities in a handful of states, polling suggests there are a significant number of undecideds. About 20 percent of voters say they have not picked a candidate, are leaning toward third-party options or might not vote at all, according to the most recent Reuters/Ipsos poll.

"On one hand, opinions about Joe Biden and Donald Trump are baked in," Christopher Stout, a professor of political science at Oregon State University, told State Newsroom. "On the other hand, there's a lot of people who aren't paying any attention to politics and this is their first time thinking about the 2024 election."

For an impression of how tight the race is, take a look at 538's newly launched election forecaster. Biden is favored to win in 506 out of 1,000 simulations of how the election could go on the site's model, while Trump wins in 491. In three simulations, no candidate wins a majority.

An April Bloomberg News/Morning Consult poll found Biden is ahead in just one of the seven battleground states, leading Michigan by 2 percentage points. Trump is narrowly ahead in Pennsylvania and Wisconsin, and more widely in Georgia, Arizona, Nevada and North Carolina.

It's the slim percentage of people who are on the fence that the Biden and Trump campaigns will be hoping their candidates can attract or reassure on Thursday evening – and discourage from voting for third-party candidates.

Robert F. Kennedy Jr and other independent or third-party contenders, such as Cornel West, failed to meet the criteria to qualify for the debate. In an election that could be decided by thousands of votes scattered in a few swing states, independent candidates could play a decisive spoiling role.

"It is Joe Biden or Donald Trump, and anyone that does anything but vote for Joe Biden is supporting Donald Trump," Biden campaign chair Jen O'Malley Dillon said on a Puck podcast this week. One of Biden's favorite sayings, "don't compare me to the almighty, compare me to the alternative," is likely to be close to his lips on Thursday.

Persuasion, reassurance and attention

In this election cycle, one uncommon issue is on many voters' minds – age. Polls suggest voters worry more about Biden's 81 years than Trump's 78, but the Republican would become the oldest ever president if he served out a second term.

On Thursday, voters will have the chance to see the men line up side by side, and both campaigns will be hoping their candidates can make persuasive arguments to undecided voters and offer reassurance that they are up to the job.

Biden has shown his capacity to shine at major events, delivering highly praised State of the Union addresses, and Trump continues to be an energetic force on the campaign trail.

Polling indicates that on policy, inflation remains a top issue of concern for many Americans, along with immigration, public safety and abortion rights. Foreign policy could have a higher level of interest in this election than in most, given the ongoing crises in Gaza and Ukraine.

Trump will likely attack Biden on immigration and inflation, while Biden will likely continue his criticisms of Trump and the Republican Party on abortion rights and the democratic process.

The former president's legal difficulties may also get a hearing at the debate, given he became the first former president to be convicted of a crime in May. Ahead of the debate, a gag order against Trump in the New York hush-money case was largely lifted, giving him more leeway to criticize trial witnesses and jurors.

With almost 20 weeks of the election campaign still to run, neither candidate will be totally defined by their performance, but the debate will allow the men to attempt to frame the contest – and be a clear marker in the race to win over the few Americans who are still undecided.

(Cover: A combination of photos taken in Columbia, South Carolina, shows former President Donald Trump (L), February 24, 2024, and President Joe Biden, January 27, 2024. /CFP)