Democratic Party leaders across the country are calling on party bosses to curtail, postpone or dramatically rethink the party's national convention scheduled for July in Milwaukee, concerned that holding a mass gathering just as levels of infection are expected to ebb could expose thousands to the coronavirus once again.

Calls from the party faithful to rethink the Democratic National Convention come as the party's presumed presidential nominee, former Vice President Joe Biden, for the first time publicly expressed doubt that the gathering could proceed as it has in the past.

"It's hard to envision that," Biden said in an MSNBC interview this week. "We ought to be able — we were able to do it in the middle of the Civil War all the way through to World War II — have Democratic and Republican conventions and primaries and elections and still have public safety. And we're able to do both. But the fact is it may have to be different."

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The Democratic National Convention is scheduled to run July 13 to 16 in a city already facing questions about whether it can accommodate 4,750 delegates, plus thousands of other party officials, corporate sponsors and journalists. Cancellation or curtailment of the national convention, the first ever held in "Cream City," could lead to millions of dollars in lost revenue. The 2016 Democratic convention generated $231 million for Philadelphia.

A Marquette University Law School poll released on Wednesday finds that 62% of Wisconsin residents believe the convention should not be held as an in-person event. Just 22% believe it should meet as scheduled.

But party leaders are increasingly resigned to the need to make big changes.

"It's more likely that it gets canceled than it happening. That's 100% true," said Alexis Wiley, a DNC superdelegate from Michigan.

A traditional convention is "out of the question at this point," said Ian Murray, a superdelegate from Pennsylvania who's attended conventions since 1992. "I don't see where we're going to be able to all gather in a petri dish in Milwaukee with the coronavirus."

Leah Daughtry, the former CEO of the 2008 and 2016 Democratic conventions, said if she were on the job again this year, "I'd be thinking about how to do a virtual convention, because you just have to — you have to consider all the options at this moment."

Contingency options could include having a "downsized convention" where only delegates attend, which would "drastically reduce" the number of attendees, she said. Ultimately, "the convention business must be done; you must elect a nominee."

How to do that remains an open question.

This account is based on conversations with at least 43 party luminaries, including voting members and staff of the Democratic National Committee, the governing body of the Democratic Party, elected officials, state party chairman and former party leaders still active in party politics. Most spoke on the record, but some were granted anonymity to speak candidly about party operations.

In response to Biden's comments, Joe Solmonese, CEO of the Milwaukee convention, said Wednesday that the challenges of the Coronavirus outbreak "require us to be deeply thoughtful about the important and unprecedented moment in which we're living."

"As we continue to put plans in place for a successful Democratic National Convention this summer, we will balance protecting the health and well-being of convention attendees and our host city with our responsibility to deliver this historic and critical occasion," Solmonese added.

Xochitl Hinojosa, communications director for the DNC, added that national party leaders are in regular touch with state parties about the details of convention planning, "and the bulk of the questions have been on changes to their delegate selection plans as we remain flexible on how they elect their delegates to the national convention."

DNC Chairman Tom Perez is receiving regular updates on convention planning and "ensuring the safety of convention attendees and our host community of Milwaukee is the top priority," Hinojosa said.

But several DNC members expressed frustration with the lack of specific guidance from convention organizers and DNC leaders about how to proceed. Some state party leaders are also grappling with how to manage their own conventions to pick national convention delegates. And while leaders understand the fluidity of the situation, virtually all of the people who spoke for this article said that the party must consider alternatives.

Perez should be "getting a ball rolling on a Plan B, and how to make sure that we can keep all of our standard procedures in place and still have an environment where we don't necessarily have to physically congregate," said Megan Green, a St. Louis alderwoman and DNC member since 2016.

South Carolina State Representative Gilda Cobb-Hunter, a DNC member and president of the National Black Caucus of State Legislators, said she's concerned that "there is no word about the potential of a virtual convention. Perhaps they have had those conversations – the leadership, the team, whoever 'they' are – but it would be nice to share that information."

"I don't know if we can adequately and accurately predict what the conditions are going to be in July," said Ron Harris, chairman of the DNC's Midwestern Caucus. He added later, "We're not necessarily getting information from the DNC every single day. Their charge has been 'Hey, business as usual — until it's not.'"

But Yvette Lewis, chairwoman of the Maryland Democratic Party, defended the lack of clarity.

"Would I love for things to move forward? Absolutely. But that's not even a consideration, nor should it be, at this point, it is how to get us out of this," she said.

And Wisconsin Democrats said they still hope Milwaukee can still reap the economic benefits of a convention.

"There's going to be a lot of companies — restaurants, bars, you name it — who aren't going to survive this...That convention can be a way to not just jumpstart them, but bring them back to life," said Khary Penebaker, a DNC member from Wisconsin.

Republicans, meanwhile, are also moving ahead with plans to hold a four-day convention to re-nominate President Trump in Charlotte from August 24 to 27.

"We continue to prioritize the health and safety of delegates, media, guests, community members and staff, and we have full faith and confidence in the administration's aggressive actions to address COVID-19," Republican National Convention spokeswoman Blair Ellis said last week, adding later that organizers "remain in communication with local, state and federal officials, and we will continue to closely monitor the situation and work with all stakeholders and health authorities to ensure every necessary precaution is taken into account."

Several Democrats said that they expect their national convention team to make safety a top priority.

Melahat Rafiei, a DNC member from California, feels that safety "is much more relevant than us getting into a convention hall or a stadium somewhere."

Representative Lauren Underwood, of Illinois, a licensed nurse who is a DNC superdelegate, said that given her position, "It's hard to consider the prospects of a national convention – a public gathering that usually brings together thousands of people – when it's not even an acceptable public health practice for millions of Americans to leave their homes at the moment."

There are signs that convention organizers are plowing ahead, cautiously.

Vicki Hiatt, chairman of the Kansas Democratic Party, said that a tour of the Milwaukee convention facilities for state party leaders scheduled for April 20 has already been postponed. Hiatt said she would rebook flights to attend if the tour is rescheduled.

"I really do want to see it happen, but you know I don't want to see it happen at the risk of people's health," Hiatt added.

But Wiley, who is also chief of staff to Detroit Mayor Mike Duggan, said she received an email last week asking her to update her online profile on a national convention member database, a sign that organizers are moving forward with some of the most tedious of logistical details. If Biden maintains his wide delegate lead over Vermont Senator Bernie Sanders, Wiley said the DNC should probably scale back.

"If nothing drastically changes in the world, it's going to be Joe Biden," she said. "Let's just move and recognize that we need to be focusing every bit of energy and money we have on beating Donald Trump."

Another point of concern for some DNC members is the long-simmering logistical headache of holding the convention in Milwaukee. Several delegations are set to lodge in Chicago, roughly 90 minutes from the convention venue, the Fiserv Forum. Multiple state party leaders expressed concern about convincing their delegations to pack onto buses for long round trips over multiple days, just weeks after public health officials urged Americans to keep their distance.

"There's going to be a serious fear factor of large gatherings for the foreseeable future in this country and that's going to be a problem for any large gathering, and that's not an unrealistic question or problem that we're going to have to contend with," said South Carolina Democratic Party Chairman Trav Robertson.

Most state parties are also struggling with how to hold their own conventions.

Several states, including Texas, Minnesota, North Carolina, and New Hampshire, are planning to hold virtual conventions instead of in-person meetings to elect national delegates, but are still finalizing details. Other states, including West Virginia, Oklahoma and Idaho, have canceled in-person conventions and are still determining how to elect national delegates.

"We are definitely looking at ways to have virtual meetings, so that we can select delegates without having everyone come to a meeting," said New Mexico Democratic Party Chairperson Marg Elliston.

The DNC is still working with state parties to determine how and when delegates will be selected. So far, three states – Kentucky, Louisiana and New York – have rescheduled presidential primaries for after the original June 9 deadline for primaries. Currently, states that hold contests after the deadline face penalties, including the possibility of having their delegate haul sliced in half.

But the DNC's Rules and Bylaws Committee is expected to meet soon to determine how to reallocate the delegates of the three states or to grant them a waiver. If the party penalizes Kentucky, Louisiana and New York, the number of delegates needed to clinch the nomination would be less than the current 1,991.

One other option being mulled by the rank-and-file: Reschedule the convention date – something that could be tricky given that the Fiserv Forum is also home to the NBA's Milwaukee Bucks, which could be in the throes of the playoffs this summer if the league opts to reschedule most of the season.

Jay Jacobs, a DNC member from New York, suggested rescheduling the convention to the week of August 17, the week before the GOP confab in North Carolina.

"The television audience will, after the trauma of COVID-19, be much lighter and less interested in watching news and politics in July, right after recovering from this upheaval," he said. Holding the meeting in August "is better for getting organized, allaying health concerns and for getting better ratings."

Others still hope the convention can continue as scheduled – with no changes at all.

"I would love it if we could [get] ourselves social distanced enough that we could flatten the curve and get together in July," said Lavora Barnes, chair of the Michigan Democratic Party. "I'm still holding out hope that we can get there."

Sarah Ewall-Wice, Zak Hudak, Nikole Killion, Aaron Navarro, Nicole Sganga, Alex Tin and Jack Turman contributed to this report.