Then-senator Jim Webb (D-Va.) speaks during a rally for President Obama in Virginia Beach in 2012. On Thursday, Webb began raising money for a possible 2016 presidential campaign. (Steve Helber/AP)

With a no-frills video and a promise to address America’s “immense and ever-growing disparities,” former senator Jim Webb of Virginia began raising money Thursday for a possible presidential campaign — presenting himself, in effect, as the first prominent Democrat ready to try to topple the supremacy of Hillary Rodham Clinton.

Webb, 68, announced by way of YouTube on Wednesday night that he was forming an exploratory committee. A Navy secretary under Republican President Ronald Reagan who served in the Senate as a Democrat, Webb said he could shake up Washington’s partisan gridlock to solve what he called “the most important question facing America today.”

“Is it possible for us to return to a leadership environment where people from both political parties and from all philosophical points of view would feel compelled to work together for the common good and to sort out their disagreements in a way that moves our country forward rather than tearing the fabric of this nation apart?” he asked.

Webb has spent time recently in early presidential caucus and primary states and in September announced that he was taking a “hard look” at a run. His 14-minute video made it clear that he was on to the next phase: seeking the huge sums of money he would need to pursue the Democratic nomination.

He did not mention Clinton or any other Democrats, but the decorated Vietnam War veteran presented himself as the antidote to politics as usual: a strong, fair-minded leader not beholden to special interests. He struck a populist note that could distinguish him from Clinton, whose close ties to Wall Street were seen as a disadvantage by 44 percent of likely Iowa Democratic caucus-goers, according to a Bloomberg/Des Moines Register poll in October.

“In politics, nobody owns me and I don’t owe anybody anything except for the promise that I will work for the well-being of all Americans, and especially those who otherwise would have no voice in the corridors of power,” he said.

Webb’s exploration was not expected to instantly shake up the Democratic field, which Clinton is widely expected to dominate if the former secretary of state and first lady decides to run. The October poll found Clinton was the first choice of 53 percent of likely caucus-goers. Webb was tied with New York Gov. Andrew M. Cuomo and former Montana governor Brian Schweitzer at 1 percent. Seventy­-two percent said they did not know enough about Webb to have an opinion of him.

Yet even political observers close to Clinton were careful not to dismiss Webb.

“He’s a formidable man. By God, an American war hero,” said Paul Begala, a Democratic operative and former adviser to Bill Clinton who now advises a pro-Hillary Rodham Clinton super PAC. “Who knows if he runs, but anybody who belittles him is an idiot.”

He added: “I have long said that a vigorous primary with quality opponents makes you a better candidate. Tough primaries create tough nominees. Just ask President Obama.”

Said J. Ann Selzer, an unaligned pollster in Iowa: “Everybody starts somewhere.”

“He has a background in the military, and he’s an economic populist. He sounds like Tom Harkin,” she added, referring to the U.S. senator from Iowa who is retiring at the end of this congressional session after 30 years.

Some political observers saw an opening for Webb. His military background gives him credibility in defense and foreign affairs, and his populism might appeal to white rural voters who have left the Democratic Party in droves, the observers said.

Some said his unvarnished style and quirky blend of liberal and conservative stances — in the video, he decried both economic inequality and “government intrusion” — could appeal to an electorate weary of focus group-tested political messaging.

The simplicity of the video, which had Webb speaking directly to the camera against a plain blue background with a few still photos mixed in, could be a selling point, said Steve Jarding, a senior adviser to Webb’s 2006 Senate campaign and a professor at Harvard’s Kennedy School of Government.

“It looked like something out of the 1980s, no bells or whistles, no B-roll or graphics,” Jarding said. “It defies conventional political handling. . . . It’s one of those things where I wouldn’t bet on Jim Webb yet, but I wouldn’t bet against him.”

Said Rep. Gerry E. Connolly (D-Va.): “The non-candidate candidate could be the un-cola of 2016.”

Others were more skeptical.

Former Ohio governor Ted Strickland, a leading Clinton supporter, shrugged off Webb’s moves, especially his populist pitch. “He is not a threat,” Strickland said. “Secretary Clinton is a fighter. She’s going to be the candidate for the little guy.”

He added: “Senator Webb is bright and capable and he has a right to do what he wants to do, but he should remember that Secretary Clinton sure has a lot of friends.”

Nathan L. Gonzales, deputy editor of the Rothenberg Political Report, questioned where Webb would fit in the pantheon on Democratic contenders.

“I just think there are a lot of question marks,” he said. “He hasn’t run a race in eight years.”

Webb has defied political odds before. Jumping in late, he pulled off a surprise win in the 2006 Democratic primary for U.S. Senate, defeating businessman Harris Miller. He went on to oust then-Sen. George Allen (R) in the general election, an upset that Allen inadvertently aided when he lobbed the racial slur “macaca” during the campaign. Webb had campaigned pushing an antiwar message and wearing combat boots belonging to a son serving in Iraq.

He served just a single term but managed to pass a monumental piece of legislation — a GI bill that expanded educational benefits. He also supported sentencing reform, an issue that could resonate with the Democrats’ African American base. Webb did not run for reelection in 2012, a decision that some saw as a strike against him.

“A lot of people will be asking, ‘Is that the reason you didn’t run for reelection, because you were still so concerned with the direction of the country?’ ” said former Virginia governor L. Douglas Wilder.

But Webb’s exit also helped him claim the mantra of outsider. Jessica Vanden Berg, a native Iowan who was Webb’s campaign manager in 2006 and is advising him now, said he never wanted to be a career politician.

“He’s not the person who is the Washington establishment,” she said. “He takes a break. It’s good for perspective.”

Webb could face stiff competition not only from Clinton but also from a growing field of possible Democratic challengers who have been maneuvering behind the scenes for months. The list includes Sen. Bernie Sanders (I-Vt.), who has been a frequent presence on television and a favorite of the left, and Maryland Gov. Martin O’Malley, who campaigned heavily for fellow Democrats ahead of the midterm elections.

Sen. Timothy M. Kaine (D-Va.), who has already announced his support for Clinton, sent out a mass e-mail Thursday that asked recipients to sign an online pledge to support her.

Rachel Weiner contributed to this report.