There is a great deal of inertia in the U.S. system and the fact that the Democrats gained many seats in the Northeast from Republican moderates means it is going to be difficult for Republicans to regain a majority.
And it could have been worse for the Republicans. An analysis of the results by the Congressional Quarterly tells us that the Republicans came within a whisker of losing many more races:
Of the 202 Republicans sworn in Thursday as members of 110th Congress, 15 maintained GOP control of their seats by margins of just 3 percentage points or less. On the other side of the aisle, just two of the 233 members of the new Democratic majority were winners of contests in which they retained their party’s control by similarly razor-thin margins.
This suggests the Democrats could easily gain more seats in 2008, especially if they win the presidency. At this point the leading candidates for the Democratic nomination, Hillary Clinton, Barack Obama and John Edwards, all look like strong choices. I do think a Democrat is likely to be elected president in 2008, especially given the tarnishing of the Republican image and reputation by the Bush presidency.