The full story is at:
http://poll.gallup.com/content/?ci=23509
1. They give Dems a false sense of security. With a 54-38 lead in the polls many Dems will let down the guard and not work as hard. After all, with that kind of lead we can't lose. Right?
2. They motivate the Repubs. If they think they're going to get crushed they will come out fighting and work hard for every vote.
3. They don't take real candidates into account. In the NOVA area Wolf and Davis are long standing incumbants who may be in for a fight this year, but I guarantee they aren't behind 16 points. People are angry at Republicans - but not necessarily their Republican.
I'm just an optimistic poll junkie is all