BURLINGTON, Vt. (AP) — An insurgent underdog no more, Vermont Sen. Bernie Sanders is laying the groundwork to launch a bigger presidential campaign than his first, as advisers predict he would open the 2020 Democratic presidential primary season as a political powerhouse.

A final decision has not been made, but those closest to the 77-year-old self-described democratic socialist suggest that neither age nor interest from a glut of progressive presidential prospects would dissuade him from undertaking a second shot at the presidency. And as Sanders' brain trust gathered for a retreat in Vermont over the weekend, some spoke openly about a 2020 White House bid as if it was almost a foregone conclusion.

"This time, he starts off as a front-runner, or one of the front-runners," Sanders' 2016 campaign manager Jeff Weaver told The Associated Press, highlighting the senator's proven ability to generate massive fundraising through small-dollar donations and his ready-made network of staff and volunteers.

Weaver added: "It'll be a much bigger campaign if he runs again, in terms of the size of the operation."

Amid the enthusiasm — and there was plenty in Burlington as the Sanders Institute convened his celebrity supporters, former campaign staff and progressive policy leaders — there were also signs of cracks in Sanders' political base. His loyalists are sizing up a prospective 2020 Democratic field likely to feature a collection of ambitious liberal leaders — and not the establishment-minded Hillary Clinton.

Instead, a new generation of outspoken Democrats such as Massachusetts Sen. Elizabeth Warren, New Jersey Sen. Cory Booker and California Sen. Kamala Harris are expected to seek the Democratic nomination. All three have embraced Sanders' call for "Medicare for All" and a $15 minimum wage, among other policy priorities he helped bring into the Democratic mainstream in the Trump era.

Acknowledging the stark differences between the 2016 and 2020 fields, Hollywood star Danny Glover, who campaigned alongside Sanders in 2016, would not commit to a second Sanders' candidacy when asked this weekend.

"I don't know what 2020 looks like right now," Glover said before taking a front-row seat for Sanders' opening remarks. "I'm going to support who I feel to be the most progressive choice."

One of Sanders' chief supporters from neighboring New Hampshire, former state senate majority leader Burt Cohen, acknowledged that some people worry Sanders is too old for a second run, although that's not a major concern of his. Like Glover, he's not sure if he'll join Sanders a second time.

"There are other people picking up the flag and holding it high, and you know, it could be Bernie, but I think there are other people as well," said Cohen, who did not attend the Vermont summit. "It's not 'Bernie or bust.' That's certainly not the case."

Another high-profile Sanders supporter who was in attendance, Cornel West, described the Vermont senator as "the most consistently progressive one out there," suggesting that some would-be 2020 candidates have adopted Sanders' words, but maintained ties to Wall Street and "militarism."

Still, West conceded that none of likely 2020 candidates "have as much baggage" as Clinton did.

Perhaps the most important member of Sanders' network, wife Jane O'Meara Sanders, said Democrats may be embracing Sanders' "bold progressive ideas" on health care and the economy in some cases, but there's need to go further on issues like climate change, affordable housing and student debt.

Whether her husband will lead the debate as a presidential candidate in 2020, she said, remains unclear. O'Meara Sanders noted that one question above all others would guide their decision: "Who can beat Donald Trump?"

"That has to be the primary goal. To win. We think you win by a very strong progressive commitment," she told AP. When asked if Sanders could win in 2020, she said "every single poll" showed that Sanders would have beaten Republican nominee Donald Trump two years ago.

O'Meara Sanders also downplayed the grueling personal demands of a presidential campaign, something that historically has led some other spouses to pressure their husbands to avoid the white-hot presidential spotlight more than once.

"It was extremely inspiring meeting all the people all over the country," she said of the 2016 campaign. "And what might be difficult for me is not as important as what might be difficult for them and whether or not we can help them with those difficulties."

"It's not about us," O'Meara Sanders added. "It's about what's right for the country."

Despite signs pointing to a 2020 run, Sanders has given himself a clear escape hatch.

Weaver, like Sanders himself in a recent interview, suggested that the senator would step aside if he believes another candidate has a better shot at denying Trump a second term. There are no clear indications from Sanders or those closest to him, however, that he currently has that belief.

"I know they haven't announced, but it sort of seems like that's what's happening," said John Cusack, another actor invited to the weekend summit. Asked about his preference for 2020, he called Sanders "the only real progressive candidate out there."

"All of the sudden, what was once fringe politics is now mainstream. Don't get me wrong, it's great that (Texas congressman) Beto O'Rourke and all these young candidates are running on the People's Summit and progressive movement platform, but let's not forget who broke us through."

"If he runs again, I'll be on board," Cusack said.