Jeff Weaver will not return as Bernie Sanders' campaign manager in 2020

Jeff Weaver, the longtime aide who led his 2016 bid, will not return to the role if Sanders enters the race, a source familiar with the planning process told CNN.

Weaver confirmed in an interview that his position will be changing, most likely to senior strategic adviser to Sanders, who is being encouraged by supporters to enter the race soon. A decision is expected in the coming weeks or months.

The move also underscores an understanding, both among Sanders' close aides and outside backers, that the Vermont Independent will need a more robust infrastructure and diverse staff in order to reach or exceed the support he received during the 2016 contest.

The source said the decision for Weaver to return in a different capacity was made well in advance of new reports about sexual harassment by staffers working on the 2016 campaign. Sanders, Weaver and the senator's campaign committee have all since expressed regret over the inappropriate behavior and pledged to provide stronger safeguards going forward.

"I am not going to sit here and tell you that we did everything right in terms of human resources, in terms of addressing the needs that I'm hearing from now, that women felt disrespected, that there was sexual harassment, which was not dealt with as effectively as possible," Sanders told CNN's Anderson Cooper last week, apologizing to "any woman who feels like she was not treated appropriately."

When asked if he knew at the time about the allegations, Sanders said he was not, adding, "I was a little bit busy running around the country trying to make the case" -- a remark even close allies worried might undermine his apology.

Sanders and his team took steps after 2016, and before his 2018 Senate re-election campaign, to tighten rules and restrictions, requiring staffers to take training courses before joining and offering them an 800-number for lodging confidential complaints.

"Whether he runs for president or not, he took seriously enough the things he heard after the 2016 campaign to put some measures in place in 2018 and that's what is most important," said Nina Turner, a close Sanders confidant and president of Our Revolution, a political action organization spun out of Sanders' 2016 success.

Weaver on Wednesday said he never intended to reclaim his title from 2016, noting that he has a teen son near college age, but said he expected to have an active role in putting together the infrastructure of a second Sanders presidential campaign.

"If he decides to run again, Bernie would have to have a campaign structure which is much more robust with a much bigger leadership team," Weaver said. "It would have to be much more diverse than was the case in 2016, when it was too male and too white."

There is no clear favorite to replace Weaver as campaign manager should Sanders proceed as expected, but a source told CNN that the process of mapping out the infrastructure for a 2020 campaign is in advanced stages. Outside organizers are planning hundreds of house parties next week as a show of organizing might -- and a nudge for Sanders to confirm his grassroots base of support remains committed.

"For many months now there have been efforts to make sure the door is open should Sanders decide he should run for President," the source said. "That involves preliminary conversations with a number of top-level people who might take senior roles in the campaign, including for campaign manager."

Shannon Jackson, a longtime Sanders ally and aide, ran the senator's successful 2018 re-election campaign. He is not believed to be a candidate for the same role in 2020.

"It was never my intention to run a subsequent campaign if there is one," Weaver said on Wednesday. "I think if you look at presidential campaign managers, the number of people who have run multiple campaigns is very few. I think I can be most helpful to Bernie, if he runs, being a strategic adviser that needs to deal with some of the 30,000-foot issues as opposed to the management of a day-to-day campaign."

Weaver had been an occasionally divisive figure within the 2016 campaign but more often in the aftermath, when he first took over as the leader of Our Revolution.

But according to a source, Weaver has been reaching out to former Sanders staff members, including those with whom he had clashed in the past, as part of an effort to repair those relationships and potentially bring them back into the fold ahead of what, should Sanders run, would be a much larger operation than in 2016.

Shortly after Our Revolution launched, staffers who had key roles on the campaign's digital and organizing teams resigned from the group amid a lingering differences with Weaver.

Kenneth Pennington and Hector Sigala, two of the staffers who left, went on to co-found the digital strategy firm Middle Seat, which advised former Texas Democratic Rep. Beto O'Rourke during his unsuccessful but captivating 2018 campaign to unseat Republican Sen. Ted Cruz.

It is unclear whether Middle Seat would work with O'Rourke again if he chooses to launch a presidential campaign.