Sen. Bernie Sanders (I-Vt.), who battled Hillary Clinton in the 2016 Democratic primary and created a revolutionary movement among millennials, is having discussions about running for president again.

"Yes, is the answer," said one Sanders associate who helped with the senator's previous bid, in response to a question about whether the Independent senator from Vermont had begun to think about another run.

"He thinks he's earned the right to run again, and he believes if he would have been the [Democratic] candidate he would have won against Trump."

The source also suggested that Sanders is making his plans with other candidates in mind.

"The last thing he's going to do is step aside and let Joe Biden take it," the Sanders associate said.

Sanders, 75, hasn't publicly said if he intends to run for president again and his office did not respond to questions.

Some of his actions, however, have people talking.

Earlier this month, he traveled to Iowa for the first time since losing the state's caucuses to Clinton during the Democratic primary. He gave a keynote address at an event sponsored by the Iowa Citizens for Community Improvement.

Next month, he'll return to the state again to promote his book, "Bernie Sanders: Guide to Political Revolution."

Sanders held campaign-style rallies in West Virginia and Kentucky earlier this month, where he criticized the Republican healthcare plan. In April, he appeared front and center on a tour across red states with Democratic National Committee Chairman Tom Perez.

Jeff Weaver, who served as Sanders's campaign manager said Sanders is "keeping the door open" for a second White House run.

Larry Cohen, a senior adviser to Sanders in 2016, said it would be good news if he ran again.

"I can speak for the millions of people who supported him in saying we would love it if he runs again, and we're hopeful he'll run again," Cohen said.

Cohen also predicted that if Sanders does run again, it will be as a Democrat.

Cohen said he doesn't believe Democrats would reject him, either, given the work he's done for the party, including through the road tour with Perez and campaigning for other Democratic candidates.

Weaver agreed.

"He's part of the Democratic leadership in the Senate and helped raise millions of dollars to help down-ballot Democrats," he said. "He's helping to reform the Democratic Party. I think it speaks for itself."

Still, the decision by Sanders to run for the Democratic nomination in 2016 as an independent is a sore spot for some Democrats. There are also Clinton supporters who believe Sanders deserves some of the blame for Clinton's loss to Trump.

Polls suggest Sanders, along with Biden, would have to be seen as favorites if they were to enter a 2020 race.

A Public Policy Polling survey out earlier this week suggested that either candidate would be the favorite over Trump.

"From what I can see, he's popular in the polls, Democrats like him and I'm sure if I was in his position I would be thinking of running for president again, too," said Democratic strategist Brad Bannon. "He certainly has true believers that would support him through hell or high water and they feel like they were robbed and destiny is on his side."

At the same time, there are also Democrats looking for fresh faces - such as Sen. Kamala Harris, the freshman California senator with a growing national presence.

Some Democrats "feel we'd be better off if we started from scratch and ran someone completely new, and I think there's an argument for that," Bannon said. "It seems to me if you're running against someone like Trump, you want someone who can run unencumbered and isn't part of the usual crowd."

The Sanders associate said the one candidate who might give Sanders pause about trying to run for the White House again is progressive Sen. Elizabeth Warren (D-Mass.), who would likely run on a similar platform.

"Some of the Bernie folks feels she would take the fire away from him," the source said.

Republicans say his age is also a factor. Sanders will be 78 in 2020.

"Sanders is too old to mount a serious campaign," said John Feehery, a Republican strategist. "That being said, his nonestablishment message still is pretty powerful, especially with the disaffected grassroots of the Democrats."

Another problem that stands in the way of Sanders's White House bid would be an FBI investigation into whether his wife, Jane, falsified loan documents while serving as president of Burlington College. The school shut down in May 2016 after going bankrupt and failing to meet accreditation standards.

Sanders has defended his wife, and said the attacks are a political smear.

"My wife is the most honest person I know," he told CNN's Erin Burnett in an interview in late June.

"It's fairly pathetic that when people are involved in public life, it's not only that they get attacked, but it's their wives and their families that get attacked."

Despite that controversy, Sanders allies say he has the momentum, and he has a head start in the 2020 race.

"He's keeping almost the same schedule that a presidential candidate would keep," the Sanders associate said. "He's doing more travel, more rallies, more for the DNC than anyone else."

"He realizes this is his moment and he's taking advantage of it," the source said.