One of the most respected independent analysts of U.S. Senate races told a group of Democrats Sunday that she's starting to think they may win enough seats this November to have a filibuster-proof majority.

Jennifer Duffy, the Senate analyst for the Cook Political Report, said that as of now, she expects Democrats to add between 4 and 8 seats to their 51-seat majority in the Senate. And perhaps even more.

"For the first time, I'm seriously contemplating the possibility of 60," she told a meeting of the Democratic Leadership Council in Chicago.

That would be a monumental achievement with profound consequences if Democrat Barack Obama also won the presidency.

It would allow the Democrats to get big proposals through the Senate over the objections of the Republican minority. The power of the filibuster, unique to the Senate, allows the minority to block anything they don't like as long as they have 41 or more votes.

If the Democrats had 60 votes, they'd have a far, far greater chance of enacting such Obama proposals as expanding health care to the uninsured, and raising taxes on those making more than $250,000 a year.

Duffy later added that the Democrats might not even need 60 votes, since they can likely attract support from moderate Republicans such as Susan Collins and Olympia Snowe of Maine on some issues, perhaps more than enough to offset the loss of support issue-to-issue from some more conservative Democrats.

"They don't need 60," Duffy said. "To be effective, they don't necessarily need 60."

A prominent liberal strategist who also addressed the Democratic group, Markos Moulitsas Zúniga of the website dailykos.com, agreed that Democrats could reach a filibuster-proof majority with fewer than 60 Democratic seats.

"The majority number for Obama to have a filibuster-rpoof majority is 57, 58," he said.

"There are seven potential Republians we can peel off on an issue by issue basis to get to that 60 vote total," he said.