Early last year, Bernie Sanders huddled with his closest advisers to talk about the future. If he ran for president again, one told him, he’d probably perform well enough in the first few states for a chance to take control of the Democratic nomination in March 2020. Then, he’d have to make some new friends — the kind he didn’t have, or seem to want, in 2016.

Sanders might end up winning crowded contests with 35 percent of the vote or less, explained then-adviser Mark Longabaugh, one of several to make presentations. Once the dust settled, Sanders would have to offer his hand to Democratic leaders he’d clashed with and consolidate the party behind him. The senator, in typical fashion, listened intently with a poker face in the private meeting, according to three attendees who, like others, spoke on the condition of anonymity. He said nothing, keeping whatever thoughts he had on the matter to himself.

More than a year later, Sanders is a second-time presidential candidate, and there is growing uncertainty among Democrats about the Vermont independent’s desire to unite a party whose fissures have deepened and multiplied since his insurgent campaign against Hillary Clinton.

In key respects, Sanders has been unable or unwilling to move beyond that bruising race, a posture that gives him a kinship with President Trump but has limited his embrace by Democrats.

He frequently revisits his biggest 2016 triumphs and obstacles in speeches. He recently criticized a Democratic-leaning think tank helmed by a Clinton ally, in part because of its conduct in 2016. And he has kept Clinton and other prominent Democrats at a distance, vexing some associates who hoped warmer relations would send a positive signal across the party.

But 2020 is shaping up as a different kind of race, raising questions about Sanders’s strategy that are becoming central to the Democratic competition. Unlike last time, he is no long shot — he’s now a leader by measures of fundraising and some public opinion polls. And this is no two-way competition — it’s become an 18-way battle royal featuring a field that is growing by the week.

Many Democrats view Sanders as a candidate for the loyal political base he built in 2016 — liberal voters enlivened by his democratic socialist crusade to take on the wealthy and powerful — which could prove valuable in a crammed field. They wonder whether he can broaden his support in the coming months and, more importantly, if he is capable of unifying the party, should he win the nomination.

“Is his support right now in excess or greater than what he got in 2018 or 2016? You know, it’s hard to say yes,” said former senator Heidi Heitkamp of North Dakota, a Democrat who served with Sanders.

Sanders’s top aides contend that any tension with Democrats arises from wings of the party overtly hostile toward the senator and his policy ideas, not the other way around. They note that he has pledged to strongly support the eventual Democratic nominee and is motivated to do what it takes to help the party defeat Trump, a point he has made publicly and privately. They are urging his skeptics to make the same commitment.

“Others who are part of the donor class need to answer: Are you committed fully, regardless of the results of the nominating process?” said Ari Rabin-Havt, chief of staff on the Sanders campaign.

The Sanders campaign recently sought to mon­etize the escalating worries traditional Democratic power brokers are beginning to voice about his rise, firing off fundraising emails in recent days as part of a 48-hour push for campaign donations. Rather than smooth concerns, he sought to capi­tal­ize on them.

“You have some of the biggest players in Washington frantically putting their heads together for how to stop us,” Sanders wrote in one of the emails. “You have career political operatives begging the financial elite for money to start new efforts to derail our movement.”

If the dynamic recalls the tone of 2016, Sanders’s campaign speeches serve as specific reminders of that race. He regularly points out that he received more votes from young people than Clinton and Trump combined. Earlier this month in Michigan, he bragged about the scope of his upset win there in the primary.

Sanders is also fond of explaining how radical some of his policy ideas were regarded back in 2016 and how they are suddenly more in vogue. “Well,” Sanders said at a rally in Wisconsin, “I think it’s fair to say that things have changed.”

For many Sanders supporters, this is precisely why he is so appealing. He is still talking about the issues he has championed for many years, with the same prickly demeanor he has long exhibited. He is combative as ever, even as he ascends the Democratic hierarchy without actually joining the party he seeks to lead.

The approach masks some small signs that Sanders is trying to make inroads among the Democratic leaders who favored Clinton’s establishment campaign last time.

In 2017, Jeff Weaver, a close Sanders confidant, met with three members of the Congressional Black Caucus at the Democratic Club in Washington, according to two people familiar with the gathering. The members were Reps. James E. Clyburn (D-S.C.), Marcia L. Fudge (D-Ohio) and Cedric L. Richmond (D-La.).

That led to a get-acquainted dinner at an Italian restaurant on Capitol Hill for Sanders and Richmond, according to one of the people, who requested anonymity to describe the private gatherings.

The Rev. Al Sharpton, a prominent black activist, had breakfast with Sanders in Harlem during the last campaign. Sanders gave Sharpton his cellphone number, Sharpton recalled, adding that he contacted the senator on such matters as the Markeis McGlockton shooting in Florida last year and efforts to repeal Florida’s “stand your ground” gun law.

Randi Weingarten, head of the powerful American Federation of Teachers and a Clinton supporter in 2016, said that she will “never forget” a conversation she had with Sanders in 2017. Sanders had heard she visited Puerto Rico following Hurricane Maria and wanted to hear what she saw, Weingarten said. She was struck by his keen interest and determination to improve the recovery effort.

“I think that was a real turning point in terms of the work we did together,” said Weingarten, who recently hosted a town hall with Sanders, the first of a number of events she hopes to convene with other candidates.

Yet Sanders also has made clear there are limits to his willingness to embrace a party structure that largely worked against him in 2016.

Last week he sent a letter to the Center for American Progress (CAP) lambasting the organization’s president, Neera Tanden, for “maligning my staff and supporters and belittling progressive ideas.”

Sanders was upset over items ThinkProgress, a project of an independent affiliated organization, published about him. His campaign manager Faiz Shakir said Sanders also “remembers from 2016” the way the organization clashed with him on policy.

Tanden issued a statement saying she had no editorial control over ThinkProgress, but she expressed concerns about a video to which Sanders objected — a gesture that helped ease strains between the two sides.

Shakir said Sanders had attended a CAP conference in 2018 to forge smoother relations, only to face what he saw as new hostility.

“He’s like, okay, well, I made an effort, and then you guys decide to go in this direction. What’s going on here?” Shakir said.

Sanders has also shown no public desire to confer with Clinton, who retains the affection of many Democrats. Many Clinton allies have remained icy toward Sanders, with some openly lambasting him in media interviews. Some Sanders allies would like to see a thaw.

“One thing that could be healthy for the Democratic Party to unify is for Senator Sanders and Secretary Clinton to meet and to articulate the common goal of defeating Donald Trump,” said Rep. Ro Khanna (D-Calif.), a national co-chair of the Sanders campaign.

There were some flashes of enmity toward Clinton in the crowds that Sanders attracted on a recent swing through Midwestern states where she lost to Trump. They complained that Clinton didn’t campaign there enough, accused her allies of trying to undermine Sanders and, in the case of one man, blurted out a profane insult with her name.

But other Sanders supporters were ready to put past conflicts to rest.

“We need to look beyond that,” said Pat McFarland, 68, a retired nurse from Croydon, Pa., who was among those cheering Sanders on at a speech in Wilkes-Barre, Pa. “We need to look at what’s best for our country.”