As Ezra Klein says it’s very doubtful that Democrats can retain 60 Senate seats over the long run. At the moment, they likely to lose a few. If the political context changes, it’s actually possible (given the 2010 map) to imagine them picking a few up. But then they’d just drop below 60 in 2012 when they have to defend the gains made in 2006. Simply put, 60 seats is unsustainable for a political party that aspires to any level of ideological coherence.
What’s also true, I think, is that as long as the GOP remains in Michael Steele / Sarah Palin / tea party mode it can’t possibly win a majority. You already saw the pre-tea GOP willfully throw the VA-Sen 2008 race to Mark Warner rather than accept a moderate nominee. The fundamental lack of any kind of pragmatic spirit whatsoever is bound to doom them.
In Beltway terms where the horse race is all that counts, this makes Steele and the hard line a disaster for the GOP. And in an sense they are. But in substantive terms it’s in many respects a huge win. The combination of the supermajority rule in the Senate and a complete and utter lack of moderation in the Republican ranks makes it impossible to get anything done. Not simply because the minority can block things, but because it’s inherently difficult for vulnerable members to vote “yes” on pure party-line measures—they lack to have some bipartisan “cover.” This is the essence of the Ungovernable America situation, and the odds are that it’s going to get worse in the future not better, unless we start seeing some support for reform of the senate.