Former Vice President Joe Biden's top donors have mixed feelings about the campaign's path forward now that it has only $8.9 million on hand going into a pivotal fourth quarter.

Some, like former Pennsylvania Gov. Ed Rendell, believe that Biden is going to have to work harder on the campaign trail with that amount of cash. But, in the end, he argues there will be enough financial resources to compete in the early caucus and primary states of Iowa, New Hampshire, Nevada and South Carolina, and then later Super Tuesday. That crucial primary day includes states that account for 40% of the total delegate allocation such as California, North Carolina and Texas.

Biden's campaign privately stressed to members of its finance committee during a conference call on Wednesday that the fourth quarter is the most important one yet as it pertains to fundraising, according to those familiar with the discussions. They also discussed ways to improve their appeal to grassroots donors, these people added.

Yet, there are other Biden financiers, who spoke on condition of anonymity, that now fear possible hurdles for the former vice president in those states and beyond if he can't turn his fundraising game around by the end of December. The total cash on hand was disclosed late Tuesday in the campaign's Federal Election Commission filing. It also showed the campaign raised just more $15 million and spent $17.6 million in the third quarter. More than $900,000 was spent on private jet travel, and millions were spent on payroll, along with other expenses.

Biden's totals lag behind Sens. Bernie Sanders and Elizabeth Warren and South Bend, Indiana, Mayor Pete Buttigieg. Their strong cash arsenals range from $33.7 million for Sanders to Buttigieg with $23 million. President Donald Trump and the Republican National Committee combined to have $156 million on hand after the third quarter.

The first four contests of the Democratic primary season are scheduled for February. Super Tuesday is set for March 3. Biden's campaign has previously signaled to its fundraisers that they need to start ramping up their efforts if they want to have the best chance at making inroads on Super Tuesday.

"Look, he's going to have to work a little harder, but I don't have a doubt he will do well on Super Tuesday," Rendell said in an interview Wednesday, while noting the Biden organization will have plenty of cash to make a breakthrough in February and March.

"I think he has to do better by the way he campaigns," Rendell said, adding that he thought Tuesday's debate was one of Biden's best performances.

Bernard Schwartz, CEO of investment firm BLS Investments who has contributed the max amount to Biden, said an $8.9 million reserve going into Super Tuesday won't be enough, yet argues big money fundraising events, along with his name recognition will get him over the finish line.

"Oh no, I don't think it's enough at all," Schwartz said. "He has some big money tickets coming in and I have every confidence we are going to make it," he added.

Schwartz said he has offered to host fundraisers in Southampton, New York, and in New York City, but the campaign has yet to agree on a date.

Other donors though are not as optimistic. They stress that the current cash-on-hand situation puts pressure on them, along with the campaign, to have a successful fourth quarter.

"He needs a big fourth quarter to be properly positioned going into the actual caucuses and primaries," a leading Biden financier explained. "Only thing our donor base can do is drive in more dollars. At this point the low hanging fruit has been harvested and we have to dig deeper," this person added.

"It's all going to count in the fourth quarter. If he doesn't have strong numbers, he's f---ing done," said another fundraiser helping Biden behind the scenes.

Another fundraiser explained that Biden's lack of cash going into the fourth quarter could put him at a "handicap" for the primary states. "We all thought he would be better than this," this max contributor said.

Biden himself brushed off any questions about the $8.9 million not being enough to maintain and pick up the extra assets he needs in order to stay alive in the race for his party's nomination.

"We got started later than anybody at all in this campaign," Biden told reporters while in Columbus, Ohio. "We did not start off by dropping $10 million from a Senate campaign, wherever that money came from," he added as a reference to Warren's large transfer from her Senate coffers to her presidential organization.

A spokesperson for the Biden campaign did not return a request for comment.

Still, skeptical bundlers of Biden's are pointing to data they say is a question mark: where are they going to acquire the big checks of $2,800 now that many in their networks have maxed out? The $2,800 sum is the most an individual can give directly to a campaign in each election cycle.

Since he entered the race in April, Biden's campaign has seen an influx of large individual contributions. Out of the $36 million it has raised, 64% was from large donations, according to the nonpartisan Center for Responsive Politics. Meanwhile, 35% of donors have given $200 or less. Compare that with Warren, who has caught up to Biden in the polls but also has at least 53% of her donors giving her less than $200. She finished the third quarter raising just more than $24 million and has $25.7 million on hand.

The primary debate on Tuesday could prove to be a key moment for Biden's start to the fourth quarter. A few of his opponents have already announced their fundraising success since the contest in Ohio.

Buttigieg spokeswoman Lis Smith tweeted that her candidate raised over $1 million in the past 24 hours from contributors in all 50 state.

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Sanders campaign announced early Wednesday that it brought in more than $620,000 from more than 40,000 contributions. Sen. Amy Klobuchar's campaign said it had its best hour of fundraising following the debate.

Biden's campaign has yet to say how much it has raised since the debate.