In 2006, Democrats led Republicans on generic Congressional ballot polling by double digits and took control of the House.  In 2008, the ground has quietly shifted — and it has accelerated in the past week.  The Hill reports that the Democrats lost half of their lead in generic-ballot polling in the past week, and that the Republicans have come close to a virtual dead heat:

Republicans have cut the Democratic advantage in the generic ballot question in half over the past week, according to a new GW-Battleground poll.

Democrats now lead by four points, their slimmest lead in more than three years. A week ago, according to the George Washington University poll, their advantage was eight points. Meantime, the congressional approval rating remained low, at 19 percent, up two points from the previous poll.

While the poll could give Republican candidates hope in a tough political landscape for the GOP, it had only mixed news for the party’s presidential candidate, John McCain. The Arizona senator remained three points behind Democratic rival Sen. Barack Obama (Ill.).

In the final weekend of 2004, the Tarrance Group (GW’s partner) put the GOP up 3 on the generic ballot — and they won a larger majority.  They have no data for 2006, but Rasmussen had a 14-point lead for Democrats, who won back control of the House as well as the Senate.  Most analysts had predicted gains for Democrats in this cycle as well — but the sudden shift gives a hint that Nancy Pelosi may have her hands full on Tuesday.

The Republicans have some hurdles here, though.  They have more retirees than the Democrats do, making it tougher to focus on pickups as much as simple holds of existing seats.  Democrats have far outraised them, too, making it harder to get the message across in the districts.

Something appears to have changed, however.  Could the divided government argument be working in a different direction?  Have voters decided to prepare for an Obama presidency by attempting to pass the House into Republican control?  It would probably take a harder swing than what we see now to make that a reality — but if this represents momentum, it may come at the right time for the GOP.