But a new organization formed by the Vermont independent to continue his political revolution across the country may be venturing into uncharted legal territory, according to campaign finance experts.
The group, called “Our Revolution,” will support progressive policy proposals and politicians across the country. According to its website, the group is operating as a 501(c)(4) organization, a tax status that will allow it to accept unlimited contributions without having to reveal its donors.
But its activities could be limited by campaign regulations because of its ties to Sanders, resulting in a highly unusual -- if not unprecedented -- political arrangement, according to Paul Ryan, the deputy executive director of the nonprofit Campaign Legal Center.
“This definitely raises, in my experience, novel campaign finance issues,” Ryan said in an interview.
Typically, 501(c)(4) organizations -- such as the Republican outfit Crossroads GPS founded by GOP strategist Karl Rove -- are run by political operatives, not elected officeholders or political candidates. They're required to primarily focus on social welfare, rather than elections and political activity.
For example, Organizing for Action, a group spun off from President Obama’s presidential campaigns, was created using the same 501(c)(4) nonprofit designation as Sanders' new organization. That group, which has advanced Obama's political agenda, has repeatedly distanced itself from electoral politics.
But Our Revolution remains closely aligned with the Vermont senator, who has asked the group's supporters to donate to the campaign of Tim Canova, a law professor challenging former Democratic National Committee chair Debbie Wasserman Schultz in her House primary.
“This race is very important for Our Revolution because if we can win this tough fight in Florida, it will send a clear message about the power of our grassroots movement that will send shockwaves through the political and media establishments,” Sanders wrote in a fundraising email.
Sanders tangled with Wasserman Schultz during the Democratic presidential primary, accusing the party's national committee of preferring Clinton for the nomination. Wasserman Schultz stepped down from her party post during the party convention in July after a leak of thousands of Democratic National Committee emails, several of which appeared to show that some staff had grown aggravated by Sanders' campaign, at some points even floating ideas about ways to undermine his candidacy.
As a sitting senator, Sanders can’t ask donors to contribute more than $2,700 each to a campaign committee per election, or more than $5,000 to a Super PAC, which can raise unlimited amounts of money but are barred from coordinating with campaigns.
Our Revolution's connection to a federal officeholder could require the group to disclose its donors and cap the amount of money it can accept from contributors under the McCain-Feingold campaign finance law, Ryan said.
“It’s a bit unusual,” Kenneth Gross, a partner at Skadden, Arps, Slate, Meagher & Flom who runs the firm’s political law practice, said of Sanders’ new organization. “I’ve not seen something constructed like this before. That doesn’t mean it’s impermissible.”
Gross, who said organizations typically pursue 501(c)(4) status to avoid disclosing their donors, said officials would have to review Our Revolution’s activities throughout the year to determine any violations.
“There’s lag time in any examination of its activities,” he said. “It’s not unusual for a 501(c)(4) to engage in partisan activities before the election, and then they can even it out with nonpartisan activity after the election.”
A representative for Sanders and Our Revolution did not immediately respond to questions about whether the group plans to reveal its donors and cap contributions. Sources close to Sanders have said that the former presidential candidate wanted to keep as many options as possible open to him in the future.
Aides to the senator said he was interested in finding a way to use his hard-earned and active email list to support down-ticket candidates this cycle, but also wanted a place to educate and mentor supporters who may be inspired to run for office down the road. In addition, he has expressed interested in backing campaigns for specific issues like opposition to the Trans Pacfic Partnership trade deal, or hydraulic fracking.
A spokesman for the Federal Election Commission declined to comment on the activities of a specific organization, but said that any group raising or spending more than $1,000 in connection with a federal election is required to register as a political committee with the commission and file reports including receipts and disbursements.
The FEC does not investigate potential campaign finance law violations unless a complaint is filed against a particular group. The commission, which is led by a six-member panel, often deadlocks along party lines when reviewing allegations.
The Internal Revenue Service and Senate Ethics Committee did not immediately respond to questions about the organization.
ABC's Adam Kelsey and MaryAlice Parks contributed to this report.