He may have made a boldface impression on recent American politics, but after 30 years in Congress, Sen. Bernie Sanders has struggled with the criticism that his legislative impact has been written in fine print — an amendment here, a symbolic vote there and many, many speeches.

But not, perhaps, for long: Sanders, just weeks from his 80th birthday, is on the cusp of leaving an indelible mark on the federal government, having shepherded a $3.5 trillion spending blueprint through the Senate this week. The legislation, backed by President Biden and Democratic congressional leaders, sets the stage for the most significant expansion of the federal social safety net in generations and the largest government response to climate change ever mounted.

“You think they will be making that criticism again if we get this done?” Sanders (I-Vt.) chuckled, after being reminded of his critics during an interview this week.

The self-described democratic socialist bristles at the suggestion that he has been a legislative lightweight — he helped orchestrate a major expansion of veterans health care in 2014 and an $11 billion investment in community health centers in 2010, among numerous smaller-bore initiatives. But he readily acknowledges that the pending legislation — which could include free community college, paid family and medical leave, universal pre-K, vast clean-energy investments and the largest-ever-proposed expansion of Medicare — outstrips them all.

“I’m proud of what we have accomplished,” he said. “But obviously this bill would be many levels above anything that I’ve ever been involved with before.”

Sanders’s Democratic colleagues — including some who had publicly minimized his legislative impact in the past — are now singing his praises, crediting him with both seeding the political atmosphere with an unabashedly liberal vision of federal government and now, as Senate Budget Committee chairman, putting that rhetoric in action.

“The fact that it has so much momentum is a huge tribute to Bernie,” said Sen. Tim Kaine (D-Va.), who shared a ticket with Sanders’s 2016 presidential rival, Hillary Clinton. “We would not be where we are in terms of talking about a package of this size and scope and impact but for two things: Bernie and a once-in-a-century public health crisis. . . . The man, the message and the moment are completely aligned right now.”

Sanders is not celebrating just yet: Not only has his budget outline not passed the House, but subsequent legislation actually turning that blueprint into law stands to be a grueling, months-long process. Already his $6 trillion ambitions had to be scaled back to accommodate more-moderate members of the Budget Committee, and other Democrats, such as Sens. Joe Manchin III (W.Va.) and Kyrsten Sinema (Ariz.), have indicated they intend to give the package an additional spending haircut.

But he remains electrified at the prospect of bringing his life’s work to fruition at what he sees as a pivotal historical moment.

“At this moment, where we have the power to do something good . . . we’re going to address them in a bold way,” Sanders said.

Republicans say they are equally elated at Sanders’s new prominence and influence over the Democrats’ agenda, signaling that they are perfectly happy to make an avowed socialist a mascot for the Biden agenda.

Lambasting the budget legislation on the Senate floor Tuesday, Senate Minority Leader Mitch McConnell (R-Ky.) called it a “reckless taxing-and-spending spree that was authored by our self-described socialist colleague.”

The National Republican Senatorial Committee and other groups have already made Sanders and his “Bernie budget” a centerpiece of their advertising, and Sen. Rick Scott (R-Fla.), the commitee’s chairman, said he did not expect that to change any time soon.

“I talk about it all the time — they’re the socialist party now, not the Democrat Party,” he said. “It’s a good message.”

Sanders’s Democratic colleagues have shown little discomfort with his role leading the budget push, and Sanders himself has complete confidence that his agenda’s popularity will overwhelm the political attacks. His schedule allowing, he said, he plans to tour conservative areas of the country in the coming weeks to promote it.

If Republicans “want to be opposed to the $300 child tax credit, they want to be opposed to expanding Medicare, they want to be opposed to expanding child care,” he said, “if they want to tell their constituents that we can continue to ignore climate change, they’re going to lose the next election.”

Sanders became a household name for railing against “million-ahs and billion-ahs” in his Brooklyn rasp, but he said his mission has now gone beyond mere wealth redistribution and an environmental rescue mission to encompass the preservation of American democracy.

“A lot of people are losing faith in democratic government, with a small ‘d,’ and it’s just terribly important to me that we show people that we understand — we have a sense of what’s going on in their lives, we can address their crises and make life a little bit better,” he said. “Maybe we can restore some faith on the part of the American people in their government.”

That is a message he took inside closed-door meetings with fellow senators, including a pair of crucial gatherings in mid-July inside the office suite of Senate Majority Leader Charles E. Schumer, where the members of the Budget panel — ranging in ideology from Sanders on the left to Sen. Mark R. Warner (D-Va.) in the center — hashed out exactly how much to spend.

“What are people demanding of us right now?” Kaine recalled Sanders arguing, noting the mounting crises of health, climate and democracy. “Are you listening to what people are saying?”

While Sanders sought to go as high as $6 trillion, Warner wanted less than half of that — especially with a separate bipartisan infrastructure deal riding alongside. Over two nights, the group struggled to reach consensus before quickly coming together late July 13 — $3.5 trillion it would be.

Sanders described the meeting as “difficult and emotional” — in part because most members of the committee sided with him in wanting a larger figure, he said, and he believes as many as 40 senators felt the same. He relented, he said, because he knew he had to.

“Everybody in the room understood that there were members of the caucus who would find it very difficult to support” a $6 trillion budget, he said. “So compromise had to be reached.”

Sanders, Schumer and Biden have all insisted that while the price tag has been scaled back, the ambitions of the legislation have not. Sanders said the $3.5 trillion budget can include every program a $6 trillion one could fit, albeit for a shorter periods of time, leaving future Congresses to extend them.

That sort of flexibility belies the criticism of Sanders’s legislative chops — doubt that was frequently sowed by supporters of his presidential rivals who were intent on making the case that Sanders was simply too radical and too inflexible to govern.

Among them was former Rep. Barney Frank (D-Mass.), a supporter of Clinton’s 2016 campaign who in several stories cast Sanders as a legislative nonfactor, a bomb thrower more interested in scoring ideological points than writing his views into permanent law.

Reached this week, Frank said he considered Sanders’s performance “the most pleasant surprise of the year” and ascribed his success to his newfound power as Budget chairman — and a sea change in political attitudes prompted by the pandemic.

“Having responsibility can make you act in a very constructive way, as Sanders is doing,” he said. “I think he is doing an excellent job.”

Also delivering praise: Sen. Elizabeth Warren (D-Mass.), a 2020 presidential rival who feuded with Sanders as they competed for the affections of liberal primary voters.

“Bernie deserves enormous credit,” she said. “Without Bernie, we wouldn’t have our toes on the line to create universal child care, expand Medicare and money to fight the climate crisis — go Bernie.”

With his ascent to power, Sanders has become as close to an integral part of the Democratic establishment as at any point in his political career.

Schumer (D-N.Y.) — a friend who attended the same Brooklyn public schools — paid tribute to Sanders this week, using the same kind of historical comparisons that Sanders himself favors.

“He kept his nose to the grindstone and led our caucus,” he said. “As a result, the Democratic budget will be the most significant legislation for American families since the era of the New Deal and the Great Society. It is big, bold change — the kind of change America thirsts for.”

Relations with the White House have been similarly warm. Biden, whom Sanders quickly endorsed after his 2020 presidential campaign sputtered, has been solicitous of the Vermonter — reflecting both a long-standing personal relationship and his key role as Budget chairman.

White House spokesman Andrew Bates said Wednesday that Biden “deeply respects Senator Sanders’s unflinching commitment to fighting for working people” as well as his “skilled leadership in helping move the legislative process forward.”

While the Senate budget has largely followed Biden’s policy blueprints, Sanders has clearly put his own stamp on the document — most notably, the dramatic Medicare expansion, adding dental, hearing and vision coverage.

A senior White House aide, who spoke on the condition of anonymity to describe private meetings, said Sanders “repeatedly pressed” Biden on Medicare expansion — including in a July Oval Office meeting with other Budget Committee Democrats. “He made that case passionately and strongly in the Oval, and the president gave his full backing,” the aide said.

Sanders’s faith in his life’s work — restoring and building on the spirit of the New Deal — is nothing new, said Tad Devine, Sanders’s former political strategist. But the recent breakthroughs on Capitol Hill, he said, reflect not only his underappreciated legislative skills but the success of a grinding, decades-long campaign to bring his ideas into the political mainstream.

“Bernie is not just lucky to be there at this moment in time — he’s worked hard to be there,” Devine said. “He’s never been somebody who shied away from really big issues and really big fights, going back to the beginning of his political career. He’s just got partners now.”

In the interview, Sanders readily credited Biden, Schumer, his Senate colleagues and a new crop of young liberal House lawmakers for coalescing around an ambitious agenda “rather than simply 2 percent here and 3 percent there.” But he was also happy to acknowledge the role that his own advocacy, including his presidential campaigns, played in popularizing that kind of ambition.

“To finally begin to see that type of transformative legislation, in which we are going to begin to address many of the crises that have been ignored for so many years,” he said, “is very gratifying.”