One thing I thought about doing the South Carolina poll over the weekend is that pretty much none of the new Republican Senators elected in 2004 are seen as vulnerable in their attempts for reelection. There is basically zero discussion about Democrats trying to win the seats of DeMint, Lisa Murkowksi, Johnny Isakson, Tom Coburn, and John Thune and although there's more about Richard Burr and David Vitter those still aren't seen as really great pick up opportunities for next year.
I'm not sure all those folks in the Republican class of 2004 are truly unbeatable. Coburn did have really impressive numbers when we polled Oklahoma back in May. Don't know anything about Murkowksi or Thune, although it does look like we'll be polling South Dakota this weekend. But DeMint sported good but not great numbers on our SC poll and most of the polling I've seen on Isakson, although there isn't a lot of it, has shown pretty mediocre approval numbers for him.
If it was a different year DeMint and Isakson at the least might be facing much stiffer challenges. But given how much Democrats have to defend elsewhere that just doesn't seem to be in the cards. The 2004 class of Senate Republicans have really had impeccable timing- they got elected in somewhat of a Republican year and they're going to stand for reelection in what is likely to be a very good Republican year. It's unlikely that a Richard Burr would have won election in either 2006 or 2008- but it's nothing new for luck to be a key determiner of whether a politician's career is successful or not.