In the House, where rules provide for strict majority rule, Democrats will have little need to court Republicans to pass most of their agenda. But in the Senate, a minority of 41 can filibuster to prevent a bill from coming to a vote. Senate Democrats will likely wind up with 58 or 59 members, depending on the outcome of a disputed Senate election in Minnesota.
The election results - by depleting moderate Republican ranks - leave the congressional GOP more dominated than ever by its more dauntless conservatives such as Sens. Jim DeMint of South Carolina and Tom Coburn of Oklahoma, who led the charge in the lame duck session that killed an auto industry bailout.
It remains to be seen how aggressively Republicans will try to wield the filibuster threat. They have recently signaled they will fight Obama's economic recovery plan if it moves too quickly. But there are political risks if the GOP is seen as obstructionist at a time when voters are clamoring for economic relief and change.
