Do you see any possible shift away, in the near-term, from our current era of highly partisan politics? What would it take to get Democrats and Republicans to actually start working together again in Congress, as they did so successfully for much of the 20th Century? My personal view is that our current era of partisanship is primarily due to problems within the Republican party; in particular, the takeover of radical hard right-wing elements and the destruction of the "RINO" wing of the party. If you agree, then maybe a better question is, what will it take for the GOP to moderate itself?OK, several premises here that I'd want to knock down.
First: did Democrats and Republicans work well together for much of the 20th century? I'd say there's a mixed bag, at best. Democrats and Republicans worked together over a 25 year stretch, more or less, to block liberal initiatives, including civil rights legislation. Complaints about gridlock and Congressional dysfunction probably peaked in around 1958-1962 -- not now.
Second, what ended that period wasn't about the GOP; it was about a realignment in which the parties wound up sorted by ideology, mainly because (very conservative) Democrats from the South shifted to the GOP.
As far as polarization being one party's fault...there are a couple of things. One is that on top of the sorting out, there's also been an exaggerated polarization in Congress, probably the most extreme in the nation's history. I also do believe, and have said, that I think there really is something dysfunctional about the current GOP. However, I'd also remind everyone that the 111th Congress (that is, 2009-2010) was one of the most productive in US history, so I wouldn't just to the conclusion that the system as a whole doesn't work based on a few bad months. Generally, I think that strong parties are generally a pretty good thing, so I'm not all that concerned that we have them -- although I'd prefer less ideological strong parties.
As far as what would get the GOP to become more moderate...the evidence over the last fifty years or so is that a Republican president would make the GOP more moderate. Other than that, I don't see anything on top that would change it.
For more, the Monkey Cage has run a lot of excellent items about polarization, but doesn't seem to have an easy link to them all (hey, John, what's up with that?). Articles I could find quickly are here, here, here, here, and here. Brendan Nyhan here. Again, I think I'd put a bit more stress than others on the current levels really being unusual, although not as historically unusual as the mid-20th century "conservative coalition" era.