Today's PPP poll has Raese up 3 in the West Virginia Senate race. This is significant for a few reasons. First, this is a seat that people thought might be in play, but with popular Governor Joe Manchin running it probably wouldn't. Second, the senator would be seated immediately. That'd give the Republicans an extra vote in a potential lame duck session.
Most importantly though, it's a very valuable seat for the GOP. Any win is a good win, but the best wins are those in Republican districts and states. To some this might seem counterintuitive. After all, this is the year to grab some blue seats. The GOP may never get another opportunity like this. That's exactly why the red seats are more valuable. Most of the blue seats will likely be lost in the next congressional or senate election.
Massachusetts-10 would be a nice win, but it skews Democratic. Republicans wouldn't stand a chance in any year but a big wave year. Add to that Massachusetts will lose a seat in the next redistricting. So it may be get even tougher for a Republican. Republicans certainly won't lose all the gains they'll make in Democratic districts, but they will be far more likely to hold Republican leaning districts than Democratic ones. And the ones a party holds for a long time are more valuable than the ones it holds only one term. The average of McCain won districts the Democrats picked up in 2006-2008 is a toss-up, while the average Obama district is Lean Democrat. That doesn't include Kansas-2, Florida-16, Texas-22, and Louisiana-6, four districts Republicans have already won back.
Of the 48 districts John McCain won that now have a Democrat 47 are considered by at least one forecaster to be in play. The lone exception is the 7th district in Minnesota. There's been no public poll on that district, so it may still come into play.
These seats may skew Republican on a Presidential level, but may have been held by a Democrat for years. In fact, 26 of the 47 are not among those that the Democrats picked up in 2006 or 2008. An incumbent can get into a seat and hold it for years, even if the district shifts its preferences. If you can knock that guy off, you'll likely keep the seat for a long time. If you fail this year, the Democrats will likely continue to hold the seat for years to come. The same holds true for the red state seats Democrats have in the senate. House and Senate seats in West Virginia and Arkansas are must gets for the Republicans.