The changes came on a day when former Vice President Joe Biden appeared to edge closer to entering the Democratic primary contest, disclosing that his family has been pushing him to join the burgeoning field.
The developments highlight the fluidity of the race for the Democratic presidential nomination, with the roster of candidates, and their top advisers, far from settled.
The team behind Sanders, who announced his run last week, is starting to look very different from the one that helped him rise to prominence as the Democratic runner-up in 2016.
Tad Devine, Julian Mulvey and Mark Longabaugh, partners in a high-profile Washington consulting firm, issued a statement Tuesday saying they would not be working for Sanders. They suggested that their strategic approach had diverged from that of the Vermont independent.
"We are leaving because we believe that Sen. Sanders deserves to have media consultants who share his creative vision for the campaign," said the statement, which did not provide details. The consultants expressed gratitude for the chance to work with Sanders.
Sanders' campaign manager, Faiz Shakir, issued a brief statement thanking the consultants and their firm. "The campaign appreciates all the good work DML has done and wishes them well," Shakir said.
The shake-up comes a week after Sanders launched his campaign with a video that went viral and a massive $6 million fundraising haul in the first 24 hours. Longabaugh and Mulvey had worked on the video, which has been viewed more than 7 million times on Twitter.
The change also comes as Sanders is set to ramp up his campaign activity. The senator participated in a CNN town hall Monday and plans to hold his first campaign rallies this weekend in Brooklyn and Chicago.
The departures raise questions about the direction of Sanders' campaign. Sanders had signaled a desire for new leadership, installing Shakir, a former national political director for the American Civil Liberties Union. In his prior presidential run, his campaign manager was longtime aide Jeff Weaver.
Shake-ups of presidential campaign teams are hardly unheard of, and many candidates go on to succeed after such events. Still, such high-profile departures early on are unusual.
As Democrats closely watch the moves of the Sanders campaign, they are also paying careful attention to what Biden will do. On Tuesday, the former vice president said for the first time that he was near a decision and had cleared a personal hurdle.
"I'll tell you straight up - we just had a family meeting, with all the grandkids, too," he told a crowd at the University of Delaware. "And there's a consensus. . . . The most important people in my life want me to run."
Biden leads in almost every public poll, but while saying he is "very close to getting to a decision," he openly questioned Tuesday whether that support would hold.
"We're also taking a hard look at whether or not this alleged appeal that I have - how deep does it run? Is it real?" he said. "I can die a happy man never having lived in the White House. But what I don't want to do is take people's time, effort and commitment without there being a clear shot that I could be the nominee."
An audience member shouted, "Just say yes!" and Biden cautioned, "I don't want to mislead you - I have not made the final decision."
While Biden weighs his options, Sanders is working to get his team in place. Tuesday's announcement means he will be separating from a firm that produced numerous ads for him in 2016, including one featuring the Simon and Garfunkel song "America" that attracted wide attention.
According to one person familiar with the conversations, the consultants reached their decision late last week, but they held off on the announcement to avoid upstaging Sanders' town hall Monday.
The person, who spoke on the condition of anonymity to describe private discussions, said the main reason for the separation was that the consultants believed they were not in sync with the direction the campaign was determined to pursue. Still, questions remain about the specific nature of the disagreement and how welcomed the consultants were in a campaign that is different from last time.
Unlike during his insurgent run of 2016, Sanders is starting as a well-known figure with an established base of supporters, while also contending with a new generation of diverse rivals who have largely embraced the views that set him apart last time. That could force Sanders to adopt a more nimble strategy.
He also has become a top target of Republicans, who are highlighting his views and positions as part of a broader attempt to portray the Democrats as far-left extremists.
Biden, a more moderate and established politician than Sanders, could shift the balance of the primary contest if he enters the race. He spoke Tuesday as part of a celebration of the newly named Joseph R. Biden Jr. School of Public Policy and Administration.
Biden, in a discussion with moderator Jon Meacham, said he has been reflecting on the last time his name was on the ballot, when he was President Barack Obama's running mate in 2012.
"Between then and now, the whole issue of social media and the use of social media has fundamentally changed," he said. "We've been getting briefings from the most advanced people in the country who run these major platforms, and telling us what we need."
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