Washington ? This time it’s really going to happen. Or so they claim.

Senators get down to work this coming week on turning ideas into legislation to cover some 50 million people without health insurance and contain costs for everyone else. Hopes are high that Democrats and Republicans can find common ground for a bill to emerge by summer.

They will have to defy history.

Grand plans to revamp health care have a half-century history of collapsing. More focused proposals, such as the creation of Medicare in 1965, have succeeded.

Lawmakers are far apart on some of the most important issues today, from the reach of government to the responsibilities of employers and individuals. And guaranteeing coverage for all could cost $1.5 trillion over 10 years, an eye-popping sum in a time of recession and mounting national debt.

Yet major constituencies often at odds are now clamoring for change. They range from consumer groups to insurers, from employers to doctors and hospitals. President Barack Obama has pledged to chip away at hardened ideological positions to find compromises.

“This is the toughest issue we have ever taken on — every part has got a chance of blowing up,” said Iowa Sen. Charles Grassley of Iowa. He is the top Republican on the Senate Finance Committee, which oversees government health programs and taxes, and plans to start work Tuesday.

Grassley said he is reasonably confident that he and the chairman, Sen. Max Baucus, D-Mont., can produce a bill that appeals to the middle. “Our only hope is if we do it in a way that keeps the vast majority of both parties going in the same direction,” Grassley said.