Sean Trende at Real Clear Politics says keep your eye on the Virginia Senate race as it could be the one that blindsides the pollsters and pundits on Tuesday:
The first scenario involves the working hypothesis I’ve used for most of this cycle: Gravity wins out. In that scenario, Democrats are effectively capped by the president’s job approval, and undecided voters break heavily toward Republicans. Indeed, most of what we see right now is perfectly consistent with this theory. Democrats tend to run a few points ahead of the president’s projected job approval in their states: They are generally polling in the low 40s in the red states, in the mid-to-high-40s in the purple states, and in the low 50s in the bluer states.
Under this scenario, we should expect to see something akin to what we’ve seen over the past few months: A gradual improvement of the GOP’s position in most races. The most prominent example of this is in New Hampshire, where Scott Brown has won over virtually every undecided voter, but you can also see a gentler version of this in the Virginia Senate race. This would be something like what occurred in 1980 and 1994, when we really were blindsided by a number of the races that broke for Republicans. If this happens, we’d see double-digit gains for the GOP in the House and probably nine or 10 seats picked up in the Senate. (emphasis added)