And it is unclear if the new powers or the rate board would have much long-term impact. The Democrats’ legislation ultimately seeks to sharply curtail the existing individual insurance market in which companies like Anthem Blue Cross now sell their policies. Instead, such policies would be heavily regulated by the federal government and sold through new insurance exchanges, where consumers could compare prices and benefits packages and choose policies that best fit their needs.

The president’s bill, like the measures adopted by the House and Senate, is expected to require most Americans to obtain insurance, and would provide new federal subsidies to help moderate-income people afford to buy private coverage.

And though Americans have heard officials in both parties talk for nearly a year about “President Obama’s health care plan,” the legislation unveiled on Monday will actually be the first comprehensive proposal put forward by the White House.

Senator Feinstein, in an interview, pointed to the $12.2 billion in profits reaped by the five biggest private insurers in 2009. “When you look at the profits in ’09, up 56 percent over the year before,” she said, “you begin to understand that something is going on that is not in the interests of the American people.”

Ms. Feinstein said that only 25 states allowed their insurance commissioners to regulate rates and that California was not one of them. “For the life of me, I am not sure why not,” she said. “The time has come for the secretary of health and human services to step into this.”

Mr. Obama has portrayed Thursday’s meeting as a chance to break the partisan gridlock that has stalled any progress on health care this year. He has called on the Republicans to come forward with proposals of their own.

But absent some dramatic turnabout by Republicans, Democratic leaders will have only one other possible path  approving changes to the Senate bill by attaching them to an expedited budget measure, precluding a Republican filibuster in the Senate. Even many Democratic lawmakers are skeptical that the complex health care legislation can be moved through using that parliamentary maneuver.