Senate Majority Leader Charles E. Schumer has been firmly repeating one simple phrase when asked about whether President Biden should step aside from his campaign: “I’m with Joe.”

But behind the scenes, the New York Democrat has left himself plenty of room to maneuver as he faces immense pressure from some Democratic senators and donors to convey a message to Biden to abandon his campaign after his faltering debate performance two weeks ago. A Thursday evening news conference in which Biden elaborated on foreign policy questions, though stumbled over some answers, hadn’t publicly changed much as of midday Friday.

“I think Chuck Schumer’s in a unique position,” said Sen. Alex Padilla (D-Calif.), one of Biden’s loudest supporters in the Senate, when asked if he believes Schumer wants Biden to stay in the race. “He uniquely among Senate Democrats is also working to ensure we maintain the majority this November. In my opinion, those two things are not at odds. … The way Chuck Schumer thinks about it might be slightly different.”

A naturally cautious leader, Schumer didn’t publicly comment following Biden’s news conference. And unlike House Democratic leader Hakeem Jeffries (N.Y.), he did not go to the White House to personally deliver a message to the president about where his members stood. But as time wears on and Biden’s political crisis continues, there are signs that Schumer’s stance may be shifting.

In a private lunch Tuesday, two of Schumer’s most vulnerable incumbents up for reelection — Sens. Sherrod Brown (D-Ohio) and Jon Tester (D-Mont.) — bluntly told the caucus that Biden would lose to former president Donald Trump, according to three people familiar the meeting. One senator made the point that even if all of Democratic incumbents won their tough races, that would still only produce a 50-50 Senate, which means Republicans would havethe majority if Biden is ousted from the White House.

“President Biden’s bad debate performance raised serious questions about whether he’s up for the job for the next four years,” Tester said in a statement after the meeting. “He needs to prove to the American people, and me, that he can do it.”

Nonetheless, Schumer is urging senators to be cautious and hold their fire as he guides them through a politically perilous moment with an unclear endgame. But he is also taking in public and private polling and data showing Biden’s effect on key swing state Senate races, according to people familiar with his thinking. It has all left some in the Senate — as well as some donors — with the impression that the majority leader is keeping the door open to a change at the top of the ticket.

Schumer is a skilled fundraiser who helped build and maintain the Democratic Senate majority. Now he has to figure out how to preserve it — or as much of it as he can — with Senate Democrats and challengers already wary of being dragged down by Biden in key states where they are outperforming him.

At times, Democratic senators have not been exactly clear where he stands on the path forward for the party. Schumer has mostly been in listening mode, they said. The usually press-happy politician has avoided the spotlight on Biden’s fate as well, as he finds himself in the uncomfortable position of no longer being closely aligned with a president who he’s worked hand-in-glove with over the past four years to pass an ambitious liberal legislative agenda.

“With something as complex as this situation, his inclination is not to stake out a bold position and then cajole the caucus to come along,” said Matt House, a former top aide to Schumer. “He likes to listen to his members very carefully, likes to facilitate discussion, and he prefers caucus unity wherever possible.”

Schumer’s top priority is protecting the five vulnerable Democratic senators running for reelection, and that’s made him wary of rushing into action on Biden, several people close to him have said. In the days after the debate, as Democrats began floating replacing Biden with Vice President Harris, Schumer encouraged senators to wait for more data before reacting publicly.

“It’s a more complicated calculus for him because you have to balance what the top of the ticket is — Biden or Harris — and then you have to go race by race,” said one person close to Senate leadership, who — like others in the article — spoke on the condition of anonymity to discuss private conversations. “He wants the benefit of clarity instead of the fog of war.”

Schumer obtained data points that show Biden’s shrinking path to 270 electoral votes after the debate, according to three people familiar with his thinking.

But it takes more time to get enough information from swing states to analyze how taking the dramatic step of changing a presidential ticket less than four months before an election would impact different Senate incumbents in diverse states.

Christie Roberts, the Democratic Senatorial Campaign Committee’s executive director, told Bloomberg News that internal data since the debate shows Senate races “holding steady or even moved a little in our direction in the last two weeks,” indicating that voters are prepared to split their ticket between races for president or Senate.

Initial data had suggested senators in Montana, Ohio and Nevada would not be helped by having Harris instead of Biden running at the top of the ticket, two people close to Senate leadership said. The political situation is incredibly fluid, however, and it will take time to see the full picture.

“I don’t think anything he does right now to add to the panic is useful,” a second person in constant contact with senators and aides said.

The majority leader is in frequent contact with White House Chief of Staff Jeff Zients and adviser Steve Ricchetti but has only spoken directly with the president once since the debate, according to a person familiar with the outreach. Congressional Democrats have complained about the lack of contact from Bidenworld in the debate’s immediate aftermath, though communication has increased. There is a sense that the White House and Biden’s top aides are too isolated from the reality of the situation, Hill Democrats said.

Biden has also made it clear that only hard data will convince him to leave the race, not the opinions of Hill Democrats, Sen. Chris Coons (D-Del.), the campaign’s co-chair, has told his colleagues. And Democrats are aware that ultimately the decision to step aside is Biden’s to make.

At the news conference, Biden said he would only drop out if the data says that “there’s no way” he can win.

“They’re not saying that,” Biden said. “No poll says that.”

So far, just one senator, Peter Welch (D-Vt.), has called on Biden to step aside — although a majority of the caucus is concerned the president cannot win in 2024, according to multiple senators and aides.

As donors and senators bombard Schumer with their concerns, he’s urged them to directly contact the White House, rather than offering to be their messenger, according to two people familiar with the conversations.

Donors are more focused on Schumer’s expensive battle to save his narrow majority. Angsty and angry large-dollar donors who want Biden to step aside are in a holding pattern, hoping to pressure the president out of the race, according to multiple people who are responsible for courting large campaign contributions. Donor anxiety is trickling down to at least one Senate campaign and to the anti-Trump super PAC American Bridge 21st Century, which have both seen the effects of a fundraising freeze, according to two people familiar with the fundraising.

Schumer, who raised hundreds of millions of dollars to win the Senate, has seemed to share donors’ concerns at times. Some donors said they believed the majority leader was open to a change at the top of the ticket, Axios reported.

“As I have made clear repeatedly publicly and privately, I support President Biden and remain committed to ensuring Donald Trump is defeated in November,” Schumer said in a statement this week.

Multiple major donors have communicated that they are increasing their commitment to Senate Democrats and have sent new six-figure donations, one national Democrat with knowledge of Senate races said. One major donor increased their support to the Democratic Senatorial Campaign Committee following the debate by 50 percent, this person said. Part of the motivation behind the increased giving was the Supreme Court’s decision on presidential immunity and the Senate’s role in confirming high court justices.

Schumer invited top Biden campaign officials Ricchetti, Mike Donilon and Jen O’Malley Dillon to talk to his angry caucus so that they could make their concerns known directly to the inner circle of the campaign. In the tense meeting Thursday, several senators expressed their deep concern that Biden could be a drag on Democrats’ chance to win the Senate.

“The polling is really what’s driving this discussion,” one national Democratic official said. “Chuck is leaning more into the position of making clear to Biden what his problems are.”

Paul Kane contributed to this report.