Sen. Bernie Sanders’ (I-VT) Monday evening Fox News town hall event was the most-watched town hall event of the 2020 campaign thus far, according to early Nielsen data. And at least four other Democratic candidates are open to participating in one of their own.

According to early Nielsen data, more than 2.5 million viewers tuned in to hear Sanders, a self-described “democratic socialist,” make his case on Fox News during the 6:30pm hour, prior to primetime. That total viewership bested CNN’s Bernie Sanders town hall event from back in February; and it doubled MSNBC’s during the same time period on Monday evening, and nearly tripled CNN’s.

The prior town hall ratings record for the 2020 cycle was a CNN-hosted event with Sen. Kamala Harris (D-CA), which drew 1.95 million total viewers.

Additionally, per Nielsen, Fox’s Sanders event brought in 489,000 viewers between the ages of 25 and 54—a key demographic for cable-news advertisers—trouncing CNN’s 281,000 tally and MSNBC’s 208,000.

The event, which took place in Bethlehem, Pennsylvania, saw the Vermont senator discuss a wide range of topics and occasionally spar with moderators Bret Baier and Martha MacCallum.

The Democratic National Committee banned the network from hosting one of its sanctioned debates, citing a New Yorker report on the network’s close ties to President Trump. But the success of Sanders’ town hall event—both in terms of ratings and the headlines generated—comes as at least four other presidential campaigns consider being involved in a similar event.

Fox News announced on Wednesday afternoon that it will hold a town hall with Sen. Amy Klobuchar (D-MN) in Milwaukee on May 8, with Baier and MacCallum once again hosting.

South Bend Mayor Pete Buttigieg is in talks to participate in a Fox News town hall, a campaign aide told The Daily Beast, and he had been prior to the airing of Sanders’ event.

Meanwhile, the campaign for Rep. Eric Swalwell (D-CA)—the latest entry into the crowded Democratic contest—said “he’s willing to do a Fox town hall, and we expect to start discussions with the network soon regarding a time and place.” Discussions about doing so have not yet begun, according to the campaign but Swalwell had previously told The Daily Beast that he makes efforts to appear on the network.

Julia Krieger, communications director for Rep. Tim Ryan’s (D-OH) presidential campaign said that he is also “willing to do a town hall with Fox News,” adding that “the campaign has reached out proactively to the network to express interest in this type of forum.” She said that the network had also reached out to them.

And Jennifer Fiore, a senior adviser to Julián Castro’s campaign, told The Daily Beast that they are in conversations with the network as well.

"He’s been a red state mayor and has always campaigned hard for every single vote on both sides of the aisle and will do the same thing in his campaign for president of the United States because everybody counts," she said.

The network had previously said they hoped the DNC would reconsider its position on hosting a debate on Fox.

“We hope the DNC will reconsider its decision to bar Chris Wallace, Bret Baier and Martha MacCallum, all of whom embody the ultimate journalistic integrity and professionalism, from moderating a Democratic presidential debate,” said Bill Sammon, Fox News’ senior vice president and D.C. managing editor. “They’re the best debate team in the business and they offer candidates an important opportunity to make their case to the largest TV news audience in America, which includes many persuadable voters.”

This story was updated to add a statement from Julian Castro's campaign and the news of Klobuchar’s scheduled town-hall event.

—Andrew Kirell and Scott Bixby contributed reporting.