That demand became part of the reelection campaign’s agreed-upon proposal to Trump this week for their two general election debates, one in June the other in September. An empty TV studio could, Biden aides feel, deprive their GOP rival of a major advantage when they face off.

“Trump feeds off the crowd, they give him life,” said one Biden adviser who was granted anonymity in order to discuss internal strategy. “We wanted to take that away.”

There were several conditions that the Biden team felt were necessary in order to agree to a debate with the former president, among them that at least one forum take place before the start of early voting and that the hosts weren’t from outlets with an ideological bent toward Trump. But in interviews with more than a half dozen officials and advisers who were not authorized to discuss private conversations, the issue of the crowd was consistent. Among their concerns were that the audience noise could disadvantage Biden, who sometimes has trouble hearing amid a din. They also wanted to ensure that there was a clean tempo and cadence to the debate and that it not turn into a shouting match or spectacle. Biden aides have envisioned using the forums to pummel Trump on abortion rights, his response to the Covid pandemic and threats to democracy. For that reason, they were also pleased that the debate would, it appears, involve microphones that can be cut off if a candidate speaks when it’s not their turn.

“I think it does matter. I mean, if you watch Trump, that is a big part of how he energizes himself,” said David Axelrod, the longtime Barack Obama aide. “And so I think that it will have some impact on him that he can’t play to the crowd and doesn’t have that kind of energy — that sort of modular energy that a crowd offers. I think that the Biden people, they won in negotiations on three points. It’s a debate without a crowd. It’s a debate without any third party candidates. And it’s an early debate. And those three things make it about as good a situation as he’s gonna get.”

While Axelrod was bullish on how the negotiations went, other Democrats have remained skittish about the prospect of Biden taking the stage with Trump at all. Many incumbent presidents running for reelection struggle in their first debate — as Obama did in 2012 against Mitt Romney — either because they have not been sharpened by the rigors of a primary calendar or rarely face tough questions from aides, or both. Trump may suffer from the same problem, as he skipped the GOP primary and rarely faces unfriendly interviewers. But the issue is present for Biden, who has largely foregone tough sit-down interviews with media outlets during his time in office. While some Democrats close to the White House suggested that Biden skip the debates entirely, most senior advisers felt he could not, for fear it would fuel public perception that Biden wasn’t up for the rigors of the job itself.

But the debates come with risks beyond Biden being out of political shape. Trump is prone to bring up unsavory topics designed to make Biden uncomfortable.

“He’ll bring up all kinds of stuff that is irrelevant and painful,” said Sen. Richard Blumenthal (D-Conn.). “He’s willing to take the hits, painful and unfair, bric-a-bracs that Donald Trump will throw, below-the belt-punches.”

Blumenthal said he believed the public would regard Trump as a “bully” for doing that again. But one way that the Biden camp felt it could avoid some of that circus — including the surprise guests — was to ensure that no crowd was allowed.

Biden aides on Thursday privately acknowledged that the debates still could fall through. That they came together at all was regarded as a surprise. Both campaigns had declared that they would not participate in the Commission on Presidential Debates’ proposed schedule. But even as it eschewed the GOP primary debate calendar, the Trump campaign reached out to television networks more than a year ago to begin gauging interest about hosting a possible debate, according to a person familiar with the outreach and granted anonymity to describe private conversations.

The Biden campaign reached out to the networks as well, while also opting against using the debate commission’s late fall schedule.

The exact nature of the president’s debate preparations is still taking shape, though former White House chief of staff Ron Klain will be involved, according to aides. Some advisers believe that Biden has a chance to get a head start in his practice, with Trump likely bogged down in a Manhattan court for his criminal hush money payment trial for at least another week. But the president’s plate is also quite full too. He is set to head overseas in early June for a trip commemorating the anniversary of D-Day and the G7 summit.

But prepping for Trump, some Democrats argue, may not be an overly complicated venture, in part because the former president often has just one speed — audience present or not.

“He is the Trump that we see outside the courtroom,” said Philippe Reines, the Democratic operative who played Trump for Hillary Clinton’s 2016 debate prep. “The Trump that we see on Truth Social. The Trump that we’ve seen during the primaries. The Trump that we’ve seen after January 6. The Trump that we’ve seen during the campaign of 2020.”

Myah Ward and Jennifer Haberkorn contributed to this report.