NEW YORK — Allies of Vermont Sen. Bernie Sanders are rallying behind the embattled presidential prospect even as they reluctantly begin to ponder the painful possibility of a 2020 campaign without him.

The 77-year-old self-described democratic socialist is the most prominent contender to face a serious setback in the evolving White House field. He’s been forced to confront reports detailing allegations of sexual harassment of women by male staffers when he sought the Democratic nomination for president in 2016.

Sanders’ loyalists expect him to launch a second campaign in the coming weeks, and his network of die-hard supporters is hosting hundreds of events across the nation this weekend encouraging him to run.

But the allegations put Sanders in an unenviable position in the early days of a contest playing out in the #MeToo era. While his competitors are visiting early-voting states and scoping out potential campaign headquarters, Sanders spent Thursday apologizing for the behavior of a handful of 2016 campaign workers and looking for a new staffers for his 2020 operation should he run.

Some allies have had their confidence shaken in the future of the man who has reshaped Democratic politics in recent years and almost single-handedly brought liberal priorities such as “Medicare for all” and free college education into the party’s mainstream.

“If he doesn’t run, there’s a massive void in this country,” said RoseAnn DeMoro, an activist and former executive director of the National Nurses United union, who reaffirmed her support for Sanders. “The passion in that base goes away. That base evaporates. It doesn’t go to someone else. There would be a void so deep it would go to (President Donald) Trump, I suspect.”

Politico reported Wednesday that in July 2016, a former senior Sanders adviser forcibly kissed a young female staffer after making sexually explicit comments. Sanders’ team said the adviser, who denies the allegation, would not be involved in a second campaign should there be one. Former campaign manager Jeff Weaver, who was made aware of some incidents after the campaign ended, would not serve as campaign manager again, although he may serve in another capacity.

No one has alleged that Sanders had direct knowledge of the incidents.

Former Sanders’ staffer Giulianna Di Lauro Velez, who alleged she was harassed during the 2016 campaign, wrote Thursday in The Intercept that sexual harassment is prevalent in many political campaigns. But she wrote that new allegations on Sanders 2016 campaign indicate “the depth of the problem was likely deeper than most knew.”

She called on Sanders to “take the rare step of setting up an independent investigation into the 2016 allegations.”

Earlier in the day, Sanders apologized, as he did last week, for the harm done under his watch and offered a direct message to women affected.

“I thank them from the bottom of my heart for speaking out. What they experienced was absolutely unacceptable and certainly not what a progressive campaign – or any campaign – should be about,” Sanders said.