The Quinnipiac poll Jason cited this morning, showing Arlen Specter in a dead heat race with Republican opponent Pat Toomey certainly isn't good news for Specter (and the polling trajectory to date is awfully unpromising), but it may not be quite as dire as it seems. As Nate Silver points out:
Toomey is much less known than Specter -- only 44 percent were able to register an opinion about him, although most of those that did thought positively of him. Usually when a candidate has poor name recognition this early in a race, it's a good sign, since it means that his numbers have more room to grow. But I'm not sure that's the case here. Currently, only 10 percent of Pennsylvanians describe Toomey as "too conservative" (38 percent describe him as "about right" and 4 percent as "too liberal"!). But Toomey is, in fact, very conservative. While previously in the House, he compiled a DW-NOMINATE score of +.768. That's a very big number; there are only four current members of the House who are to Toomey's right.
Again, Specter is hardly where he'd like to be in these polls--especially given that the whole reason he left the GOP was so that any matchup with Toomey would be before the full Pennslvania electorate rather than just its shrinking Republican base. But my expectation is that Toomey will prove too conservative for the state as a whole once it gets to know him.