Former Gov. Martin O’Malley of Maryland, who has been promoting himself to Democrats as a potential alternative to Hillary Rodham Clinton in the 2016 race for the White House, on Sunday spoke out against the possibility of a dynastic rematch between Mrs. Clinton and Jeb Bush.

“The presidency of the United States is not some crown to be passed between two families,” Mr. O’Malley said on ABC’s “This Week.”

Until now, Mr. O’Malley’s refusal to attack Mrs. Clinton outright has prompted detractors to suggest that he was running more for vice president than to be the party’s eventual nominee.

On Sunday, Mr. O’Malley said repeatedly that “new perspectives and new leadership are needed.”

And he said that Democrats needed to nominate someone who was willing to take on “wealthy special interest groups.” Asked if Mrs. Clinton fit that description, Mr. O’Malley demurred.

“I don’t know where she stands,” he said. “Will she represent a break with the failed policies of the past? I don’t know.”

Mr. O’Malley was among Mrs. Clinton’s earliest supporters in 2007, and had seemed to take her side recently when she was widely criticized for her use of a private email account as secretary of state, saying earlier this month that he was “a little sick of the email drama.”

On “This Week,” Mr. O’Malley pointed to his own executive experience as governor and mayor of Baltimore, each for two terms. He lamented the influence of Wall Street in politics and called for a return to economic populism. And he called for a president with “the ability to get things done rather than put their finger in the wind and looking for popularity.”

But when asked when he would announce his campaign, Mr. O’Malley smirked, saying: “I will make a decision this spring.”