The warning signs for Joe Biden are flashing from all directions.

On the debate stage Tuesday night, he frequently faded to the background as his Democratic rivals turned their attention to Sen. Elizabeth Warren, a clear sign of her new stature at the top of the field. Mayor Pete Buttigieg and Sen. Amy Klobuchar spent the night shouldering into his center-left political lane, arguing for the kind of pragmatism that had been his calling card.

And then came the revelation that Biden’s campaign account has shrunk to $9 million on hand, less than half of what Warren, Buttigieg, and Sen. Bernie Sanders had.

Combined with questions about his son’s business dealings and Warren’s rise in polls, Biden is facing perhaps the most difficult period yet of his presidential campaign, a time when he appears stuck in neutral while Warren powers ahead.

The fund-raising results reinforced the sense of a shift. When Biden entered the race in April, he collected $6.3 million on his first day, propelled partly by a high-dollar fund-raiser with many of Philadelphia’s Democratic players. It was taken as a sign of the institutional support underpinning his campaign.

But Biden finished fourth in fund-raising in the three months that ended Sept. 30, and is now fifth when it comes to money in the bank, according to campaign disclosures posted online Tuesday night. Campaign cash is often seen as a measure of support (how many people like a candidate enough to fork over hard-earned dollars?) and it’s vital to staffing early-voting states where organization and voter contact are critical.

“For the candidate who was supposed to be the electable front-runner, dominant name in the field, to have this weak a cash-on-hand report I think is a problem,” said Mike Lux, a consultant who lived in Iowa for decades and is neutral in the primary, but worked on Biden’s 1988 presidential campaign in the state. It might be especially worrisome for Biden, “who has a big staff, who is running a campaign that’s heavily investing in TV and mail.”

High-profile Biden supporters in Philadelphia said Wednesday that they’re not worried.

“There’s no panic or even extreme concern,” said David L. Cohen, the executive vice president of Comcast and a Biden fund-raiser and supporter who hosted that April event.

“He was never going to stay untouchable at the top of the polls," Cohen said. "With everything that has happened... I think it’s pretty remarkable how strongly his numbers have held.”

Campaigning in Ohio on Wednesday, Biden contested the idea that he is no longer the front-runner (the most recent averages of national polls show a virtual tie, or Biden with a lead) and seemed to welcome the scrutiny that fell on Warren.

“It’s kind of about time other people get questioned,” he said.

In a separate appearance, he stressed Warren’s repeated dodges about whether she would raise taxes to expand Medicare to all Americans. “It’s fascinating that the person who has a plan for everything has no plan for the single most consequential issue in this election," Biden said.

(Warren has said overall costs, including taxes and health care, would fall for middle-class families, but has refused to acknowledge that tax hikes are part of the plan, even though Sanders has said they are.)

Biden also hit back at Trump’s Ukraine attacks with his most forceful response yet, saying he made no money as vice president other than his salary, while Trump continues to conceal his private interests. “Mr. President, release your tax returns, or shut up," Biden said.

Alan Kessler, another local Biden fund-raiser and a Center City attorney, noted an unanticipated cost this cycle of running TV ads punching back at Trump’s false claims about Biden in Ukraine — another sign of how that controversy has dragged on the former vice president, even though the underlying accusations are unsubstantiated.

Biden’s campaign spent more in the last quarter than it raised.

“They ran ads on something they felt they had to run ads on, something they hadn’t planned on two months ago," Kessler said, adding he thinks that shows a campaign able to “hit fastballs but also curveballs.”

While Pennsylvania insiders have rallied around Biden, arguing that he is the candidate best positioned to win moderate voters and key swing states, his reliance on big donors partly explains his drop-off in fund-raising. Supporters who boosted Biden early by giving the maximum allowed now can’t contribute any more. He is scheduled to return to northeastern Pennsylvania for a fund-raiser Tuesday and one in Pittsburgh in November.

Candidates such as Warren and Sanders, meanwhile, rely far more on small donors who haven’t hit the maximum and can keep giving.

Biden’s latest report shows that only about a third of his fund-raising in July, August, and September came from people who have given $200 or less. For Sanders and Warren, more than half of their support came from people in that category.

“I don’t think this debate will change much in the polls,” said former Pennsylvania Gov. Ed Rendell, a top Biden supporter who has organized fund-raisers for him.

But with Warren surging and Biden largely standing still, Buttigieg and Klobuchar sought to take advantage Tuesday. Each was sharper and more aggressive than in previous debates, and took aim at big, liberal policy ideas, arguing that they would offer more practical solutions that could actually become law.

Buttigieg, of South Bend, Ind., and Klobuchar, of Minnesota, say their Midwestern backgrounds would boost their appeal in the critical states such as Pennsylvania, Michigan, and Wisconsin that Biden has often emphasized.

When Warren accused other Democrats of trying to “dream small,” Klobuchar hit back, arguing that there is a difference between a plan and a “pipe dream.” She said her brand of politics could win a place such as Ohio, which hosted the debate. Buttigieg had several strong exchanges, including with former Texas Rep. Beto O’Rourke on gun control.

A survey by the 538 website and pollster Ipsos found Klobuchar and Buttigieg had the biggest gains in terms of whom voters said they would consider voting for following the debate.

Leslie Anne Miller, a Pennsylvania attorney and frequent contributor to Democratic candidates has donated to both Biden and Klobuchar. Biden, she said, is the “sentimental favorite -- don’t get me wrong -- but I’m interested in a candidate’s strengths overall and I think it’s still early.”

City Councilman Allan Domb, who gave the maximum to Biden but has not endorsed him, said he was impressed with Klobuchar and would consider her.

“I liked the way she handled herself," he said. "It was very presidential.”

Buttigieg, who has a Philadelphia fund-raiser scheduled for Sunday, quickly rose from obscurity early in the primary but has plateaued in recent months, while Klobuchar has failed to gain traction and is still fighting to qualify for the next debate, in November.

“Their best strategy is for them to position themselves as the best moderate alternative in the race if Biden is fading,” Lux said.