New challenges arise for Joe Biden's fundraising efforts following the debate.

• After the June debate, President Joe Biden's fundraising operation is encountering new obstacles.
• Some of Biden's campaign bundlers have stopped raising money for him because they are uncertain if he will be the Democratic nominee.
• Some Biden supporters have withdrawn their donations, believing Biden should exit the presidential race.

Almost 10 days after his poor presidential debate performance, President Joe Biden's fundraising operation began to falter.

According to sources, some of Biden's campaign bundlers have ceased contacting potential donors following the June 27 debate.

A well-connected Democratic fundraiser, who raises money for Biden and the Democratic Party, stated that no one is picking up the phone. These individuals were granted anonymity to discuss private conversations on a sensitive topic.

Some of his fundraisers are only reaching out to people in their personal networks, after receiving no response or furious replies from those who questioned why they should donate to Biden following his debate performance, according to sources.

Bundlers are essential to any campaign's financial strategy. These affluent and well-connected individuals personally ask for donations from their social and professional networks.

Bundling is a skill that involves asking for financial contributions from friends, family, clients, and colleagues for a candidate who shares one's values. Some bundlers only ask for small amounts, while others feel comfortable asking for six-figure checks. The key is to use personal capital to ask for favors.

Bundlers are a crucial indicator of a campaign's momentum: If a candidate is gaining traction, bundlers will enthusiastically promote the campaign to their friends and family. However, if a candidate is struggling, bundlers may withdraw their support before it reaches the campaign staff.

Despite what the president says, some of Biden's bundlers are considering pausing their efforts because they are uncertain about his long-term commitment to the race.

John Morgan, a longtime ally and Biden fundraiser, stated that he will not raise any more money or write out checks until he is certain that Biden is the candidate and the campaign has set a date for his planned fundraiser.

To reassure my donors that Biden will remain in the presidential race, Morgan stated that the upcoming weeks will be crucial.

Other donors are withdrawing their support because they believe the president should withdraw from the race.

According to Stewart Bainum Jr., the chairman of Choice Hotels and a major Biden donor, it is now best for the country and the world for him to pass the baton, as it will be a disaster for the country if he stays in the race.

Bainum stated in an interview Monday that we will assist the nominee, whoever that may be, after the convention, but not before.

Last year, Bainum, who hosted a fundraiser for Biden in Maryland, predicted that Biden would drop out of the race before the convention and that the nominee would be chosen by delegates.

"We want to know who the nominee is. We believe there should be an open convention and the delegates should have the power to decide," he stated.

According to Federal Election Commission records, Sandy Bainum and her husband, Bainum, have each donated the legal maximum of $929,600 to the Biden Victory Fund, which supports the campaign, the Democratic National Committee, and numerous state parties.

If Biden does not withdraw, Bainum predicts that Trump will win again, ending any possibility of Democrats winning the House or Senate majority.

A Biden campaign spokesman did not return a request for comment.

According to a RealClearPolitics polling average, Biden was trailing Trump by 3.3 percentage points as of Monday in a general election matchup.

Over the weekend, a new Bloomberg/ Morning Consult poll revealed Trump's lead over Biden in crucial battleground states, including Arizona, Georgia, Nevada, and North Carolina.

In Michigan and Wisconsin, the poll showed Biden leading by 5 and 3 points, respectively.

Some donors have expressed hesitation to continue supporting Biden, according to former Pennsylvania Gov. Ed Rendell, who has been actively fundraising for him since the debate.

Philadelphia attorney Lisa Kabnick, a retired partner at Troutman Pepper, has already given at least $25,000 to Biden's political operation and committed to giving at least $10,000 more after the debate, according to FEC records.

CNBC did not receive a reply from Kabnick regarding her plans to donate to Biden.

If Biden's political operation experiences a decline in fundraising in the near future, it would represent a significant shift for the president, who has been a successful fundraiser for his own campaigns and the Democratic party for many years.

In June, Biden's campaign team announced that they had raised $127 million, with over $30 million coming in after the debate. The overall Biden reelection effort, comprising campaign committees, allied groups, and the Democratic National Committee, began July with $240 million in cash on hand.

Despite Biden's attempts to convince party donors that his poor debate performance was a one-time occurrence, some of them remain uneasy, as he struggled to complete sentences, follow his train of thought, and counter Trump's attacks.

The efforts to quell donor concerns appears to be having mixed results.

On Monday, Biden had a call with several of his major donors, campaign manager Jen O'Malley Dillon, and Maryland Governor Wes Moore. The call began 35 minutes late, as per a source on the call.

On the call, Biden affirmed his intention to continue his campaign, disregarding doubts from certain donors about his chances of defeating Trump, according to two sources.

Biden's poor debate performance prompted him to plan to "attack, attack, attack, attack" Trump during the second debate in September, according to one source. The call lasted approximately 30 minutes.

Despite criticism from party donors, including Disney family heiress Abigail Disney, who plans to halt donations until Biden drops out of the race, Biden remains unfazed.

"In a surprise appearance on MSNBC's "Morning Joe" on Monday, Biden stated, "I don't care what millionaires have to say. As a matter of fact, you don't see many of them supporting Trump.""

Despite some concern among Democratic donors, there are still many who are willing to support the president.

Glen Tullman, CEO of Transcarent, stated that he is fully supportive of the president and intends to continue giving, despite his imperfections. He emphasized that the alternative is unacceptable, not just for Democrats, but also for independents, progressives, and traditional conservative Republicans.

In March, the founder of Livongo Health donated $450,000 to the Biden Victory Fund, as per FEC records.

There are also several fundraisers for Biden being planned across the country.

According to a source, Biden plans to participate in a fundraiser in Austin, Texas on July 15, the same day he will give a speech at the LBJ Presidential Library.

This individual stated that he will also be traveling to California and Colorado for a fundraising swing at the end of the month, which will be co-hosted by businessman Tim Gill, real estate executive Wayne Jordan, and his wife, longtime Democratic donor, Quinn Delaney.

Neither Gill nor Jordan responded to CNBC's request for comment.

Rendell announced plans for a September fundraiser for Biden in Pennsylvania, while Biden's allies in New York are also planning a September fundraising event, a source revealed.

If polls show him ahead of Trump, those who had initially refused to donate money may start giving him funds again, according to Rendell.