The Gang of Six is back:

The president appeared in the White House briefing room hours after the “Gang of Six” briefed senators on its plan to cut the deficit by $3.7 trillion over 10 years, in part by raising $1 trillion in new revenue. Obama’s decision to align himself with the Senate package aims to further marginalize House Republicans, who have resisted any debt plan that includes new revenues.

“We have a Democratic president and administration that is prepared to sign a tough package that includes both spending cuts, modifications to Social Security, Medicaid and Medicare that would strengthen those systems and allow them to move forward, and would include a revenue component,” Obama said. “We now have a bipartisan group of senators who agree with that balanced approach. And we’ve got the American people who agree with that balanced approach.”

The introduction of a bipartisan deficit-cutting plan, which was negotiated over the past seven months, revived hopes yet again of striking a “grand bargain” ahead of the Aug. 2 deadline to raise the debt limit.

But with only two weeks remaining, its late entry into the debt negotiations could derail the proposal.

There are reportedly over 50 senators–and perhaps as many as 60–on board with the plan. With Bill Clinton ratcheting up pressure on Republicans Monday evening by implying Obama has the constitutional option available to him, a precious few conservatives may finally be coming around to a sane deal.

President Obama praised the development, calling the plan “a very significant step” toward “the potential for bipartisan consensus,” as the plan is “broadly consistent” with his desire for a package that mixes big spending cuts with revenue raisers without gutting Medicare and Social Security.

But Obama’s very public triangulation–a willingness to, Bill Clinton style, ostentatiously undercut his own party’s priorities–is earning him some (expected) flak from the left:

“While details are sketchy, the “Gang of 6″ proposal appears to ask seniors, the middle class and the poor to bear the burden of deficit reduction, with cuts to Social Security benefits, billions in stealth cuts to be named later, and no real effort to make corporations and millionaires pay their fair share….We cannot allow a minority of Tea Party led Republicans in the House to hold our nation’s economy hostage in order to protect tax breaks for the rich and corporations, while forcing cuts to programs families depend on. The President and Democrats in Congress must stand up for everyday Americans and not give into politicians more interested in protecting their corporate backers than ensuring our economy recovers,” said Justin Ruben, executive director of Moveon.org.

“This terrible plan could cut Medicare and Medicaid to unsustainably low levels and put seniors’ well-being at risk. Anyone who wants to pass it through Congress should remember that more than 70 House Democrats have already pledged their opposition, and more are signing on every day,” intoned co-chair of the Congressional Progressive Caucus Rep. Raúl M. Grijalva of Arizona.

Watch for a Nancy Pelosi statement on the deal–her House caucus is dominated by the Progressive Caucus to a much greater extent than when Dems had the majority (most of those who lost their reelection bids were conservative Blue Dogs) and many of their votes will be needed for any deal that brings more money into government coffers, even if it does so through a net tax decrease.