What is wrong with the Congressional Democrats?

The Center on Budget and Policy Priorities comments that

Changes reportedly made last night in the stimulus package would reduce its effectiveness as stimulus. Although the package includes a reasonably designed tax rebate, the two most targeted and economically effective measures under consideration — a temporary extension of unemployment benefits and a temporary boost in food stamp benefits — were zeroed out, apparently at the insistence of House Republican leaders.

What is wrong with the Democrats? They control both houses of Congress. They should be able to pass their own stimulus package without having to negotiate with the Republicans. If the Republicans filibuster it or the President vetoes it, it will be their necks. Given the panic about the economy, they wouldn't dare.