WASHINGTON — Day-old Presidential contender Bernie Sanders said that questions about the Clinton Foundation’s activities are fair game in the race for the Democratic nomination, and noted that Hillary Rodham Clinton has yet to take a position on contentious trade legislation and the proposed Keystone XL Pipeline.

At a news conference with the U.S. Capitol as a backdrop, the independent senator from Vermont said creating “an economy that works for all of our people” would be at the center of his campaign for the Democratic nomination.

“The wealthiest people in the country and the largest corporations” must stop shipping jobs overseas and start paying their fair share of taxes, he said.

He spoke not long after filing papers for his launch and as his team came out with a new website. It says, “A political revolution is coming,” and has a disclaimer that it is “paid for by Bernie 2016, not the billionaires.”

Sanders said he remains a political independent, but drew a tweeted welcome to the race from Florida Rep. Debbie Wasserman Schultz, head of the Democratic National Committee. “Sanders has clearly demonstrated his commitment to the values we all share as members of the Democratic Party,” she posted.

And Clinton tweeted: “I agree with Bernie. Focus must be on helping America’s middle class. GOP would hold them back. I welcome him to the race.”

He is the first major challenger to enter the race against Clinton, who launched her own bid for president earlier this month and is the heavily favored, early front-runner in the Democratic contest.

Former Maryland Gov. Martin O’Malley and former Virginia Sen. Jim Webb are potential contenders, and ex-Rhode Island Gov. Lincoln Chafee recently said he intends to run.

On economic issues, Sanders’ campaign platform coincides with positions taken by Sen. Elizabeth Warren, D-Mass., a fierce critic of large corporations, who has declined calls to enter the presidential race.

He hopes to turn a lingering sense of economic insecurity on the part of millions of Americans into votes in primaries and caucuses that begin early next year.

Once known as a socialist mayor of Burlington, Vt., Sanders is a native of Brooklyn with an accent to match. The 73-year-old veteran lawmaker said he has never run a negative television commercial, implying he won’t this time, either. Yet he said, “We’re in this race to win,” and pledged a vigorous debate on the issues with Clinton, a former first lady, senator and secretary of state.

Drawing a contrast with his rival — if politely — he said he opposed the Iraq war while in the Senate, a conflict that she voted to authorize as a New York senator.

He also said he is helping lead opposition to legislation that would strengthen President Barack Obama’s hand in future trade talks, including a proposed 12-nation Trans-Pacific Partnership.

He added he opposed legislation to permit construction of the proposed Keystone XL Pipeline that cleared Congress and was vetoed earlier in the year by Obama.

“We don’t know what Hillary’s stances are on all of the issues,” Sanders added.

Clinton has supported previous trade deals, and the issue emerged as a key point of contention eight years ago when she and Obama both sought the presidency.

She’s expressed skepticism recently about the emerging Pacific agreement, saying it must protect U.S. workers, but has not taken a firm position on the deal and spoke in its favor when in Obama’s Cabinet.

Sanders said questions about the Clinton Foundation are legitimate for the campaign ahead. The global charitable effort was set up by former President Bill Clinton after he left office.

Critics have recently raised questions about possible connections between donations made by foreign governments and policies Hillary Clinton pursued while serving as Secretary of State.

In addition, the acting head of the foundation said recently the organization expects to refile some of its past tax returns to correct errors.

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By David Espo, AP Special Correspondent. AP writer Dave Gram in Burlington, Vermont, contributed to this story