First, he lost his clear lead in the polls over the rest of the record-setting field of Democratic presidential contenders.

Now, former Vice President Joe Biden has been eclipsed by three of his rivals for their party’s 2020 nomination in the crucial race for campaign cash.

Democratic strategists say the "devastating number" is a clear warning sign for Biden as he battles to be his party's 2020 standard-bearer.

WARREN, SANDERS, FAR AHEAD OF BIDEN IN DASH FOR CAMPAIGN CASH

Even the candidate acknowledges the deficit.

“We haven't raised what a lot of people have -- we got started way later than everybody else, but we’ve raised, this last quarter, $15 million, in the middle of summer,” Biden said Thursday at a fundraising event in Palo Alto, Calif.

The $15.2 million the former vice president brought in during the July-September third quarter of fundraising was down more than $6 million from the $21.5 million he raised in the April-June quarter.

Perhaps more telling is the fact that it is far behind the $25.3 million that Sen. Bernie Sanders of Vermont collected in the past three months, and the $24.6 million that Sen. Elizabeth Warren raised. Warren, the populist senator from Massachusetts, has surged in recent months, in donations and surveys, and is now essentially tied with Biden for the lead position in most recent national and early-voting-state Democratic nomination polls.

For the second straight fundraising quarter, Biden was also outraised by South Bend, Ind., Mayor Pete Buttigieg, who took in $19.1 million in contributions to his campaign over the past three months.

THE LATEST FROM FOX NEWS ON THE 2020 PRESIDENTIAL CAMPAIGN

“This is a devastating number for Joe Biden,” said a Democratic strategist who asked for anonymity in order to speak more freely.

With the kickoff primary and caucus voting just four months away, the strategist emphasized that “this is a time when candidates are supposed to be showing momentum and strength going into the early contests. This number shows that his operation is basically treading water and being left behind by more dynamic campaigns.”

Another Democratic consultant, who also asked to remain anonymous, warned that Biden’s fundraising figures “should raise some serious questions about whether Joe Biden has the chops to raise the money necessary to compete in a general election and whether he can excite the Democratic base that is giving is giving an enormous number of small-dollar contributions to other candidates.”

A longtime friend, adviser and fundraiser for Biden cautioned against reading too much into the third-quarter figures.

“I’m relatively happy with the Biden numbers. Obviously they could always be higher,” said Larry Rasky, who was a senior adviser on Biden’s unsuccessful 1988 and 2008 White House runs.

Rasky said that raising funds wasn’t “the top priority of the campaign” over the past three months, as staffers concentrated on building up grassroots support.

“I think the numbers give them what they need to compete and try and win in February,” he added. “Third quarter numbers are tough historically for candidates and a candidate like Joe who may not have as big a grassroots base as Sanders and Warren. But the number [will] get us there.”

And he predicted a more robust fundraising effort for the already-underway fourth quarter, spotlighting “it feels that way to me already. There’s more intensity as we start the quarter off.”

Biden has spent the better part of the primary season to date fending off attacks not only from President Trump, but from an array of primary rivals eager to take him down a peg. His poll numbers have remained strong in the face of it all, even as Warren's have risen. One question mark for Biden going forward involves his connection to the newly launched Trump impeachment inquiry on Capitol Hill.

Trump is under fire from Democrats over his July 25 call with Ukrainian President Volodymyr Zelensky, in which he urged Zelensky to investigate the Biden family over their business dealings in Ukraine. Critics say this amounted to seeking foreign assistance in a U.S. election.

But it's also cast a spotlight on the Bidens. Biden’s son Hunter served on the board of a Ukrainian energy company while his father was vice president. Trump and fellow Republicans have questioned Biden's role pushing for the dismissal of a Ukrainian prosecutor who had been looking into corruption at the company (though the prosecutor was viewed by officials in several countries as himself corrupt).

While Biden denies wrongdoing, a recent Monmouth University poll indicated that 43 percent of registered voters believe Trump’s claim that Biden did pressure Ukrainian officials to keep them from investigating his son’s business ties, with 37 percent not buying the president’s allegations and one in five unsure. The survey also spelled trouble for Trump, with just four in 10 registered voters continuing to say that the president should be reelected, compared with 57 percent who say it’s time to have someone new in the White House.

Biden may soon have some outside help, however, as he battles for the Democratic nomination.

Two sources close to an effort to form a pro-Biden super PAC tell Fox News that the outside group could be formed in the coming weeks.