Biden falters in high-stakes debate, Trump spews falsehoods

Heading into tonight's event, Biden and Trump are locked in a close contest. 538's presidential election forecast rates the race as a dead heat, with both Biden and Trump having about a 1 in 2 shot of winning the election. This falls in line with our national polling average, which has the two candidates just about tied at 41%, with Kennedy polling at 9%.

But as readers know, U.S. presidential elections aren't decided by the national popular vote. Instead, they're decided by the Electoral College, where the results in individual states determine who wins each state's electoral votes, with a majority of 270 out of 538 in total necessary to claim victory. Currently, the forecast shows an extremely tight race in each of the most pivotal states.

For instance, Biden's path to victory may rest primarily on winning the Frost Belt battlegrounds of Michigan, Pennsylvania and Wisconsin that he carried in 2020. While the forecast shows him with small leads in each of those states, Biden's advantage is well inside the range of potential outcomes, meaning Trump could easily carry them once we get to November. Meanwhile, Trump holds a narrow edge in the Sun Belt swing states of Arizona, Georgia, Nevada and North Carolina, but similarly his leads are far from secure.

Still, with nearly four months to go until Election Day, there's a great deal of uncertainty around where public opinion will stand when voters cast their ballots. 538's forecast utilizes a combination of polling information and campaign fundamentals, such as the economic situation and each state's partisan leanings. Together, those indicators show a toss-up race that could go in either direction.

Now, tonight's debate could move the contest: Historically, the margin in presidential races has shifted by an average of about 2 points in the two weeks following the first general election debate in cycles dating back to 1976. In what could be bad news for Biden, that movement has more often than not gone against the incumbent president or party. Yet we're still sailing in uncharted waters. After all, this election involves both a sitting and former president, an unprecedented matchup in modern times. The debate is history-making, too: It's nearly three months earlier than any past general election face-off.

-538's Geoffrey Skelley

Hours before the debate, first lady Jill Biden told deep-pocked donors that the president is "ready" for his faceoff against Trump.

"Joe's ready to go. He's prepared. He's confident," she said at a fundraising retreat at the Ritz-Carlton in downtown Atlanta, according to the press pool. "You know what a great debater he is."

She thanked donors for "making the right choice" for democracy, urging them to keep up their work in support of Biden, according to the press pool.

"We can't stop now. We can't get complacent," the first lady said. "We've got to keep working together, working harder than we've ever worked before."

-ABC News' Fritz Farrow, Gabriella Abdul-Hakim and Will McDuffie

The White House Correspondents' Association is "deeply concerned" that CNN has barred travel pool reporters from being inside the studio and close to Biden during all of tonight’s historic presidential debate.

Despite "repeated requests" for White House pool access, CNN will allow only one print reporter to enter during a commercial break for a brief observation.

"That is not sufficient in our view and diminishes a core principle of presidential coverage," president of the WHCA Kelly O’Donnell said in a statement Thursday.

"The pool is there for the 'what ifs?' in a world where the unexpected does happen,” O’Donnell said.

-ABC News' Emily Chang

Just because their microphones will be turned on only when it's their turn to speak, it doesn't mean there won't be interruptions, and campaign staffers of both candidates are preparing for it.

Since the candidates are still only 8 feet apart, there is a scenario where the viewer may not hear an interruption, but the other candidate and the moderators will.

Advisers from both campaigns told reporters that's something they've acknowledged or discussed in debate preparations.

3:02

Biden and Trump to square off on debate stage with no audience, muted microphones

The debate will not feature an audience and microphones will be unmuted only when it is a candidate's turn to speak. ABC News' Rachel Scott reports from Atlanta.

The Biden campaign said it is hoping the president just flat-out ignores any distractions or comments that Trump makes.

The Trump campaign said it is aware that tonight they could play this both ways: The former president could stay on message when his microphone is turned on but make off-hand comments to irk Biden when his microphone is turned off.

When it comes to the traditional handshake between the candidates before the event, both sides are being coy.

One Biden adviser said, "I wouldn't do it," while an adviser for the Trump campaign responded simply by laughing.

-ABC News' Rachel Scott