• House Democrats are circulating a drafted letter urging the Democratic National Committee to slow down the nomination process for President Joe Biden, which could begin as soon as Sunday.
• As of Tuesday, at least 19 Capitol Hill Democrats had come out publicly to urge Biden to bow out of the race, following his debate fumble against Donald Trump in June.
• Biden's mission to rescue his campaign with a flood of public appearances is competing with the turbocharged energy of the Republican National Convention, days after the attempted Trump assassination.

House Democrats are circulating a letter for signatures that urges the Democratic National Committee to slow down its nomination process for President Joe Biden.

The letter asks the DNC to cancel its plan to hold a "virtual roll call" to officially nominate the president. This process could begin as soon as Sunday, weeks ahead of the Democratic convention where the nominee is typically voted on in person.

"Stifling debate and prematurely shutting down any possible change in the Democratic ticket through an unnecessary and unprecedented 'virtual roll call' in the days ahead is a terrible idea," the letter read.

The letter has received over 20 signatures so far, including from Reps. Jared Huffman, D-Ca., Mike Levin, D-Ca. and Susan Wild, D-Pa., two sources told NBC News.

Huffman is one of the several members leading the effort to rally signatures, a spokesperson for his office confirmed to CNBC.

"Rep. Huffman and other members are very concerned with this extraordinary attempt to speed up the nomination, and do not think brute force is the way to achieve enthusiasm," the spokesperson said.

The signers have a diverse range of stances on Biden's reelection bid, the sources said. Levin, for example, has openly called on Biden to bow out of the race while Wild has not yet commented publicly.

The DNC decided to move forward with the virtual roll call approach in May, accelerating the nomination timeline to meet the Aug. 7 deadline to get its nominee onto the ballot in Ohio, a state that has become more of a Republican stronghold in recent years.

Ohio has since moved its ballot deadline to the end of August, but the DNC has maintained its expedited nomination plan.

In the drafted letter, House Democrats said that without the legal justification of the Ohio ballot deadline, the sped-up nomination process would be viewed as a "purely political maneuver."

Despite Capitol Hill's concerns, the DNC doubled down on the virtual roll call decision in a statement: "The suggestion that the timeline for the virtual roll call has been accelerated is false. The timeline for the virtual roll call process remains on schedule and unchanged from when the DNC made that decision in May," the DNC said.

The Biden campaign also stood by the virtual roll call plan during a Tuesday press conference in Milwaukee.

"I think the answer here is very simple, it is the fact that, you know, there have been virtual roll calls in previous presidential elections," Biden's deputy campaign manager Quentin Fulks said. "Ohio Republicans decided to play games...It is our obligation as a campaign to make sure that President Biden is on the ballot."

The letter comes as some Democrats continue to call on Biden to bow out of the presidential race following his weak debate performance in June against former President Donald Trump. As of Tuesday, at least 19 Capitol Hill Democrats have come out publicly to urge Biden to bow out of the race.

Other lawmakers have issued more tepid statements, leaving the public to read the tea leaves of their stances on Biden as the party's nominee. Still, others have hidden their Biden concerns behind closed doors.

California Rep. Adam Schiff, for example, told donors in a private meeting on Saturday that Democrats would lose both the Senate and the House if Biden remained in the race, according to a Tuesday New York Times report.

Despite the pressure from Democratic lawmakers, donors and strategists, Biden has defiantly pledged to stay in the race.

"Fourteen million people voted for me to be the nominee in the Democratic Party, okay?" the president said in a Monday interview with NBC's Lester Holt. "I listen to them."

The NBC interview was part of a larger campaign push to rescue Biden's political future with more public appearances.

Over the past several days, however, Biden's media junket has been largely drowned out by the attempted assassination of Trump at his Saturday rally in Pennsylvania where one attendee was killed and two others were critically injured.

The horrific shooting has further turbocharged the energy of this week's Republican National Convention where the GOP is fervently rallying around its newly solidified presidential ticket: Trump and his running mate, Ohio Sen. JD Vance.

Meanwhile, with the Democratic Party split on Biden's political future, the lawmakers' letter draft to the DNC said the party needs more time to sort out its presidential ticket, and that an expedited nomination process would undermine that effort.

"It could deeply undermine the morale and unity of Democrats – from delegates, volunteers, grassroots organizers and donors to ordinary voters – at the worst possible time," the letter read.

"The Democratic Party must nominate its presidential ticket at the Democratic National Convention, in regular order, as we always have," the letter continued.