Wednesday’s Senate passage of a $3.5 trillion spending plan is seen by congressional experts as further evidence of Vermont independent Sen. Bernie Sanders’ shift from “rebel with a cause” outsider to leading Democratic deal-maker.

“If 10 years ago somebody would have said to you that Bernie Sanders was a team player, you would have been laughed out of the United States Senate,” said Ross K. Baker, a distinguished professor of political science at Rutgers.

But now, Baker said, Sanders is indeed acting as a team player in his push for the $3.5 trillion budget resolution that passed early Wednesday morning in the Senate on a 50-49 party-line vote.

On Monday, Fox News — long viewed as a nemesis of the self-described Democratic socialist — published an op-ed by Sanders that made the case for why more moderate or conservative voters should back the ambitious spending plan, which includes a provision for higher taxes on the very wealthy.

And it wasn’t a one-off. Over the past several months, the three-term Vermont senator has appeared on local news channels and sat for interviews throughout the country — often in areas with high concentrations of more conservative voters.

Sanders has criticized Fox News in the past, but in his column this week he appealed to the network’s right-leaning readers as he made the case for the $3.5 trillion plan backed by President Joe Biden. The senator — who just over a year ago while facing Biden in the Democractic primary campaign ran ads criticizing the eventual nominee’s rejection of Medicare for All — has gone to bat as chair of the Senate Budget Committee to push forward legislation alongside the president.

“He’s on the team of somebody who is ideologically quite different, but I think he understands the gravity of the situation,” said Baker, the Rutgers professor.

This type of political compromise is a marked change for Sanders, who has historically cast himself as a political outsider. His 2015 memoir is called “Outsider in the White House,” and for years he was dismissed by some Democratic lawmakers as too radical.

“The big transition wasn’t from Rep. Bernie Sanders to Sen. Bernie Sanders, it was from Sen. Bernie Sanders to Chairman Bernie Sanders,” Baker said.

Mark Haskins, senior fellow at Georgetown University’s Government Affairs Institute, emphasized that as chairman of the Budget Committee, intra-party compromise is now in Sanders’ job description.

“The chair writes 95% of the bill,” said Haskins. “Bernie wrote 95% of this bill with input from other senators, but he’s the one who puts forward that first document. Then his job is to sell it.”

Sanders chaired the Veterans Affairs Committee from 2013-15, which Haskins thinks marked his move away from his “rebel with a cause” outsider image, toward that of a politician willing to make sacrifices to pass legislation.

“I think he recognized at that point it’s one thing to be an outsider and make a lot of noise, it’s something else to be a member of the Senate and get something done,” said Haskins.

The complex budget reconciliation process allows the Senate to pass legislation by way of a simple majority vote instead of having to overcome a filibuster that requires 60 votes.

“As chairman of the Senate Budget Committee, Sen. Sanders is playing a leading role in writing and passing the most consequential legislation for working people, the sick, the elderly and the children since the Great Depression,” said Mike Casca, Sanders’ communications director, in an emailed statement.

Sanders’ appeal to a wider audience is not just aimed at conservative voters.

“While you see him doing all this stuff in the press to sell it to the general public, he’s really trying to pressure the senators, because he only needs to find 50 other people to say yes to his product,” said Haskins. “He’s able to get folks in the general public to assist with that by calling their senators and amplifying that message.”

Because reconciliation is immune to the filibuster, the Budget Committee chair only has to appeal to enough members of one’s own party to get their resolution through. And in this case, that means appealing to the voter base of all Democratic senators. That’s what Haskins thinks Sanders is doing on Fox News.

“Some conservative Democrats like (Sen. Joe) Manchin (of West Virginia) and (Sen. Kyrsten) Sinema (of Arizona) have to flip Fox viewers to get elected. Bernie knows that if Fox viewers vehemently hate him, it’s going to be tough for Manchin and Sinema to support his bill. If you know there are gonna be people against you, you’d prefer they are against you without passion,” said Haskins.

In other words, Sanders may be looking to mitigate the passion of the conservative voter base’s opposition to him, rather than to actually sway conservative voters, Haskins said. Because if moderate swing voters in Arizona only mildly disapprove of Sanders rather than vehemently, Sinema can more easily support him.

The next step for the budget resolution is to the House of Representatives, where Rep. Peter Welch, D-Vt., will have a chance to amend and vote on the bill.

In an interview two weeks ago, Welch was emphatic in his support for the American Families Act, the formal name of the reconciliation effort. “It’s all about human infrastructure,” he said. “It’s about child care, family leave, two years of community college, two years of pre-K. The budget reconciliation is extremely important.”

If the House makes any changes to the bill it will be returned to the Senate for another vote. House Majority Leader Steny Hoyer announced Tuesday that the chamber would return from its current recess on Aug. 23, which is earlier than previously planned. When representatives return from recess they will vote on the reconciliation bill.