For Democrats who had hoped to lure Massachusetts Sen. Elizabeth Warren into a presidential campaign, independent Sen. Bernie Sanders might be an intriguing candidate.

Senator Sanders, who is opening his official presidential campaign Tuesday in Burlington, Vermont, aims to ignite a grassroots fire among left-leaning Democrats wary of Hillary Rodham Clinton. He is laying out an agenda in step with the party's progressive wing and compatible with Senator Warren's platform — reining in Wall Street banks, tackling college debt, and creating a government-financed infrastructure jobs program.

"I think our views are parallel on many, many issues," Sanders said in an interview with The Associated Press, describing Warren as a "good friend."

Sanders caucuses with the Democrats in Washington and is running for the Democratic nomination. He and Democratic former Maryland Gov. Martin O'Malley are vying to become the primary alternative to former Secretary of State Clinton. Much of the energy behind a Clinton alternative has been directed to drafting Warren, but she has repeatedly said she won't run.

For Sanders, a key question is electability. Clinton is in a commanding position by any measure. Yet his supporters in New Hampshire say his local ties and longstanding practice of holding town hall meetings and people-to-people campaigning — a staple in the nation's first primary state — could serve him well.

"Toward the Vermont border it's like a love-fest for Bernie," said Jerry Curran, an Amherst, New Hampshire, Democratic activist who has been involved in the draft Warren effort. "He's not your milquetoast left-winger. He's kind of a badass left-winger."

A self-described democratic socialist, Sanders has raised more than $4 million since announcing in early May that he would be a presidential candidate. He suggested in the interview that raising $50 million for the primaries was a possibility. "That would be a goal," he said.

He rejects the notion that he's simply in the race to shape the debate.

"Hillary Clinton is a candidate, I am a candidate," Sanders said. "I suspect there will be other candidates. The people in this country will make their choice."

Whether Sanders can tap into the party's Warren wing and influence Clinton's policy agenda remains unclear. But he has been on the forefront of liberal causes as Clinton has seemed to be tacking to the left.

Clinton regularly refers to an economic stacked deck against American workers — rhetoric that offers comparisons to Warren's frequent description of the economic system being "rigged" against middle-class families.

Sanders has joined with Warren to drive opposition to the Trans-Pacific Partnership trade proposal, arguing it would ship jobs overseas. Clinton has avoided taking a specific position on the trade deal.

The Vermont senator has introduced legislation to make tuition free at public colleges and universities, a major piece of Warren's agenda. The free tuition would be covered by a mix of state and federal money and paid for by higher taxes on Wall Street investment firms, hedge funds, and other financial transactions. Clinton's campaign has signaled that she intends to make debt-free college a major piece of her campaign.

Sanders' disdain for big money in politics is also shared by liberals. Clinton frequently tells voters that she would back a constitutional amendment to overturn the Supreme Court decision allowing super PACS to raise unlimited money. But Democratic super PACs are already lining up behind her.

"I'm not going to have a super PAC in this campaign," Sanders said. "I don't go to fundraisers where millionaires sit around the room and say here's a million, here's $5 million for your super PAC. That's not my life. That's not my world. And I think the American people are saying that is not what our politics should be about." He said the money he's raised so far has come from more than 100,000 individual donors, giving an average of $42 each.

Organizers of the pro-Warren effort say Clinton may still win over many of their supporters. Charles Chamberlain, executive director of Vermont-based Democracy for America, said Sanders would "fill the void" for some of the voters hoping for Warren to run. But not for all.

"They're different people. They've got different pluses, they've got different minuses," Chamberlain said. "Some of the people who want to see Elizabeth get in the race are going to Hillary. Some of them are going to go to Martin O'Malley." O'Malley is expected to announce his candidacy Saturday.

If Sanders is the underdog, that's fine by him. During the 1970s, he lost four statewide elections as a third-party candidate, and then narrowly defeated a Democratic incumbent in 1981 to become Burlington's mayor.

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"Nobody — trust me — nobody thought I would defeat a five-term incumbent Democratic mayor," Sanders said, noting the winning margin of 10 votes.

The lessons, he said, are clear: "Don't underestimate me."