The GOP is currently 19 seats short of a filibuster-proof majority, but this year polling averages suggest that the party is currently set to pick up 8 seats. Then in 2012, scores of Democrats are up for reelection: in California, Florida, Hawaii, Maryland, Michigan, Minnesota, Missouri, Montana, Nebraska, New Jersey, New Mexico, North Dakota, Ohio, Pennsylvania, Rhode Island, Virginia, Washington, and Wisconsin.
The GOP just cannot win some of these seats, e.g. Hawaii, but if the Republicans are strong enough to take the White House in 2012, they will probably be on the attack in many of these states. I count 12 seats in states that either went for Bush in 2004 or for which Bush was campaigning heavily. An R+5 year could tip many of these seats to the GOP. So, it’s possible.
But this also means that every seat counts. Mike Castle voted against ObamaCare, and he has co-sponsored the bill to repeal it. Is he really worth going after? A pickup of 19 seats in two years is a monumentally difficult task. It seems to me that at a time when the party needs every seat it can get, Castle can get one.