Democratic presidential nominee Hillary Clinton campaigns with Sen. Bernie Sanders of Vermont last month in Durham, N.H. (Melina Mara/The Washington Post)

Sen. Bernie Sanders, a loyal soldier for Hillary Clinton since he conceded the Democratic presidential nomination in July, plans to push liberal legislation with like-minded senators with or without Clinton’s support if she is elected — and to aggressively oppose appointments that do not pass muster with the party’s left wing.

In an interview, Sanders said he and other senators have started plotting legislation that would achieve many of the proposals that fueled his insurgent run for president, including a $15 federal minimum wage, tuition-free public college, an end to “mass incarceration” and aggressive steps to fight climate change.

The senators, Sanders said, also plan to push for the breakup of “too big to fail” banks and to pressure Clinton to appoint liberals to key Cabinet positions, including treasury secretary. Sanders said he would not stay silent if Clinton nominated the “same old, same old Wall Street guys” to regulatory positions that are important in enacting and overseeing the financial policies he supports.

“I will be vigorously in opposition, and I will make that very clear,” Sanders said.

Sen. Bernie Sanders said that if former rival Hillary Clinton focuses on the issues, that will improve her standing — not just with millennials but with Americans in general. (Reuters)

Sanders’s comments signal that, if she wins the presidency Nov. 8, Clinton may have to contend not only with Republicans who oppose her agenda but also with liberals in her party who were not excited by her campaign and have long feared that she plans to govern as a centrist.

It remains to be seen how much sway Sanders will have in January. He is in line to take over the chairmanship of one of the Senate’s major committees if Democrats regain control of the chamber, but aides to some of the senators he said are working with him suggested that less of a coordinated effort is underway.

The proposals Sanders plans to push are contained within the Democratic Party’s 51-page platform, a document that he and his allies were instrumental in drafting in the run-up to the party’s July convention in Philadelphia. Although in the past the party platform has often been quickly forgotten, Sanders’s role in shaping it was key to his decision to support Clinton, and he has long planned to pressure her to follow through with action in the White House.

Progressive groups have questioned whether Clinton will fully embrace such initiatives as president and where they might fall on her priority list, particularly as she potentially faces a divided Congress and makes outreach to Republicans a focus of her campaign. Clinton did not embrace some of the policies contained in the party platform as a candidate in the primary cycle, but she has since signaled her support.

Sanders said he considers it his job “to demand that the Democratic Party implement that platform.”

The iconoclastic senator from Vermont, whose long-shot presidential campaign turned him into a national celebrity, shared his plans Friday during a candid and lengthy interview in his home town.

In recent weeks, Sanders has stumped for Clinton, traveling the country to rally skeptical progressives and others around her bid to defeat Republican nominee Donald Trump. But during the conversation in his office here, it became clear that Sanders is ready to reassert himself within the Democratic Party.

“The leverage that I think I take into the Senate is taking on the entire Democratic Party establishment, and, you know, taking on a very powerful political organization with the Clinton people,” Sanders said. “We won 22 states and 46 percent of the pledged delegates, 13.4 million votes . . .and a majority of the younger people, the future of the country. . . . That gives me a lot of leverage, leverage that I intend to use.”

Sanders said that his office and others have started converting the party platform into draft legislation. He said the lawmakers “informally” working with him include Sens. Elizabeth Warren (D-Mass.) — who campaigned with Clinton on Monday in New Hampshire — Sherrod Brown (D-Ohio) and Jeff Merkley (D-Ore.).

Aides to those senators said they are certainly inclined to embrace liberal agenda items, many of which they have championed in the past. And Warren, in particular, has a history of speaking out against President Obama’s nominees when they are not up to her standards, and she has signaled a willingness to do so under another Democratic president.

Sanders said he has not sought assurances from Clinton or her staff that she would be on board with an effort to enact the platform “piece by piece,” as he intends.

But, he said, “right now, as I see it, that platform is where Clinton is at, where I am at, where the vast majority of Democrats are at, and that is what we’ve got to implement.”

The Clinton campaign has sought to play down any potential fissures with the left wing of the Democratic Party. On Sunday, Clinton spokesman Brian Fallon said that Clinton is “proud to have worked with Senator Sanders on drafting the most progressive platform in Democratic Party history.” If she is elected, Fallon said, Clinton “intends to partner with him to advance their shared priorities.”

During a rally in Raleigh, N.C., on Sunday, Clinton touted her proposal to make college debt-free — and credited Sanders with working with her on the idea. The two rivals had worked together after the primaries to scale back Sanders’s proposal to make public colleges and universities tuition-free for everyone.

But in other ways, Clinton has signaled that her early agenda may be designed to appeal as much to Republicans as Democrats. On Sunday, Fallon told reporters in Raleigh that Republicans should be able to support two of her top priorities, immigration reform and investing in the country’s infrastructure.

“We think that we have put forward ideas for the first 100 days that are the ones that Republicans should have every reason to work with us on,” he said.

Sanders said in the interview that he favors a more combative approach.

“It’s not good enough for me, or anybody, to say, ‘Well, look, Republicans control the House: From Day One, we’re going to have to compromise,’ ” Sanders said. “The Democratic Party, before they start compromising, has got to rally the American people around our ideas and make it clear that if Republicans do not go along with reasonable ideas to benefit the middle class and the working class, they are going to pay a very heavy political price.”

If the Democrats take over the Senate, Sanders is all but guaranteed to have a bigger voice in the chamber. He is in line to become chairman of the Budget Committee, although he said his preference would be to take the gavel of the Committee on Health, Education, Labor and Pensions, which has jurisdiction over the minimum wage, health care and many of the issues he has championed during his quarter-century in Congress.

Sanders said Clinton’s appointees to top positions in her administration would provide a strong indication of the direction she intends to take — and he plans to hold her feet to fire to fill her Cabinet with progressives. A top priority, he said, is a treasury secretary who does not come from Wall Street.

Like other progressives, he said he has been troubled by rumors that Facebook chief operating officer Sheryl Sandberg could be under consideration for that post.

Sandberg, Silicon Valley’s best-known female executive and author of a best-selling book on women’s empowerment, has a close relationship with former treasury secretary Lawrence H. Summers, who has ties to Wall Street.

“I personally believe that a billionaire corporate executive is frankly not the kind of person that working families want to see as secretary of treasury,” Sanders said. “We need somebody who has a history of standing up to Wall Street and is prepared to take on the financial interests whose greed and illegal behavior has done so much harm.”

Sanders said he also will make known to Clinton his views about who should serve in roles such as U.S. trade representative and attorney general.

“I expect her to appoint people who will head agencies in a way that is consistent with the Democratic Party platform, and if not, I will do my best to oppose those nominees,” he said.

Sanders characterized the platform as more progressive than Clinton’s campaign agenda but said she would have an obligation as the party’s president to try to enact it, regardless of which party controls the House and the Senate.

“On a number of positions, her views are progressive,” Sanders said, “but I believe that the Democratic platform is more progressive and that the Democratic platform is the most progressive platform in the history of this country.”

Sanders will get another opportunity to promote his agenda next month, when he launches a 17-city tour in support of his new book, “Our Revolution: A Future to Believe In.” Sanders also has plans for a string of television appearances to tout the book.

The first half of the book, he said, is a recounting of his presidential campaign from a “very personal point of view.” The second half details many of the policy issues he pushed on the campaign trail, but in “much greater detail.”

The book tour, Sanders said, “will be a good place, I think, to begin talking about where we want to go as a country.”

During the course of the interview, Sanders, 75, first hedged when asked whether he would ever run for president again, but then he declared it as “highly, highly, highly unlikely.”

Wagner also reported from Raleigh.