Cunningham's decision not to comment on the most recent allegations is part of a nearly week-long move underground since news about his text message affair with Guzman Todd was first reported. He canceled an appearance at a virtual forum scheduled for Monday afternoon, and his campaign also stopped running any paid advertisements on Facebook on Monday. He has not posted anything on Twitter since Friday.

Cunningham also postponed a fundraiser scheduled for Tuesday evening on Zoom, according to an email from his campaign obtained by POLITICO. In the email, his campaign did not say when the fundraiser would be rescheduled.

The revelations about Cunningham's affair are just one of several developments that have thrown a race in which the Democrat led consistently for the past few months into chaos. Tillis revealed last week that he tested positive for Covid-19 and is in quarantine. Cunningham's campaign said over the weekend he tested negative for the virus, but he continues to quarantine because he debated Tillis in person last Thursday, one day before the incumbent's positive test.

Both parties are fighting hard over the North Carolina seat — it's seen as a likely linchpin for the majority in January — in what has become the most expensive Senate election this year.

Cunningham, in the statement from Friday, said he "hurt my family, disappointed my friends, and am deeply sorry." He asked for privacy for his family, but added that "in the remaining weeks before this election I will continue to work to earn the opportunity to fight for the people of our state." His campaign did not elaborate further on Tuesday and has not responded to multiple requests to answer followup questions about the matter.

His national allies, including the Democratic Senatorial Campaign Committee, continued to stand by Cunningham.

"North Carolinians are supporting Cal because he will protect health care coverage for pre-existing conditions, bring down the costs of prescription drugs and focus on providing additional aid to those impacted by the pandemic," said Lauren Passalacqua, a spokeswoman for the DSCC. "Nothing can erase Sen. Tillis' failed record of working to overturn the Affordable Care Act, blocking Medicaid expansion and refusing to extend unemployment relief as North Carolinians remain out of work — and unfortunately for Republicans, that's what this election is about."

Republicans quickly attacked Cunningham over the affair. Senate Leadership Fund, a super PAC run by allies of Majority Leader Mitch McConnell, released a TV ad Tuesday featuring local news clips talking about the affair, with a narrator pointedly asking what else Cunningham was hiding.

Tillis, in an interview on Fox News Channel Tuesday morning, said Cunningham "owes the people of North Carolina a full explanation."

"His family should be kept private," Tillis said. "He’s got teenage children. But Cal owes North Carolinians, all the voters, a full and thorough explanation" for his personal behavior.

"As this scandal unravels, Cal's refusal to quickly come clean leads to serious questions about his honesty and trustworthiness," Jesse Hunt, a spokesman for the National Republican Senatorial Committee said in a statement. "He won't be able to put this scandal to bed any time soon now that voters know he's willing to hide the truth to protect his political career."

Democrats were rattled by the revelations about Cunningham. For months, Cunningham had held a narrow but stable lead in the race, and Tillis had struggled to consolidate support from his own base. But the details about Cunningham's affair give Republicans new opening to attack the Democrat's character and fitness for office in the closing stretch of the campaign.

One Democratic consultant familiar with the process, who requested anonymity to speak candidly, expressed frustration and said national Democrats backed Cunningham over other potential candidates who had been interested in the race because he was viewed as the candidate with the fewest vulnerabilities for Republicans to exploit.

Still, there were no calls on Tuesday for him to exit the race. Wayne Goodwin, the chairman of the state party, said in a statement that the election would be "about which candidate will stand up for North Carolina and protect our health care." He criticized Tillis' record and expressed confidence Cunningham would prevail.

Other Democrats in North Carolina expressed frustration and disappointment with Cunningham's behavior — but said it did not change their stance in the race.

"We're disappointed, and we don't condone his behavior. But working people have a lot more important things on their minds than these text messages," said MaryBe McMillan, president of the North Carolina AFL-CIO, which endorsed Cunningham. She reiterated the position even in light of the new reporting Tuesday. "We've got our jobs, our unions, our very lives on the line in this election — and when you look at these issues, Cal continues to be the voice for working people."

Karen Ziegler, who leads a grassroots group called "Tuesdays with Tillis" that is affiliated with the national group Indivisible, said earlier Tuesday she stood by Cunningham despite the text revelations, and that members of the organization had expressed that sentiment during their meeting earlier in the day. Ziegler said she donated $50 to Cunningham's campaign after the texts became public last week — and sent him another $50 Tuesday evening after the latest revelations.

"[Tillis is] a complete disaster for the people of North Carolina and this country," Ziegler said. "And if you compare the policy differences with these texts, it's a no brainer. Everyone has to vote for Cal Cunningham."