John Emerson points me to some interesting data crunching over at Open Left. The diarist, "dreaminonempty," is analyzing the past few years' election results against demographic variables. What's there not to like? Though I do think the perspective is a bit too The Emerging Democratic Majority. Yes, it does look like the Republicans, as a white Christian party, are in a world of demographic hurt. But, be cautious about projecting current trends too far. By that, I mean that the trends working against the Republicans are clear, but we aren't quite where the Republicans were during the 1970s-1990s where the opposition party had to play on their terms (e.g., the two Democratic Presidents were Southerners who engaged in triangulation). Realignments take time, and by the time all the dynamics play out some of the background assumptions may have changed.
More substantively, below is a comparison of the proportion of votes that the Republican John C Fremont received in 1856, and the proportion of whites who voted for Barack Hussein Obama in 2008 (the % county-by-county here is an estimate since Exit Polls are only statewide).
My conclusion by inspection is that Yankees, the whites of Greater New England, were willing to vote for "Black Republicans" in the 1850s, and they were willing to vote for a black Democrat in 2008. It would be nice to generate an r-squared, by I don't have the original data sets handy right now.
I'd be happy if the argument were true, but I read an almost identical argument in a book written around 1959 - 1960 (part of the Kennedy pre-campaign): Bowles' "The Coming Political Breakthrough". He just totted up the demographics of the then Republican and then-Democratic groups and projected, and the Democrats looked invulnerable.
By 1968 two major demographics had moved away from the Democrats: urban Catholics and Southern whites, and for the last 40 years the Democrats have been trying to recover.
People complain about the two parties not standing for anything and not coming through on their promises, but essentially that's what the two party system is for. The purpose is to prevent a clear decision between strongly different alternatives, where 51% of the voters can completely change things. The goal is for each party to mush together a coalition making up from about 47% to about 53% of the electorate. If either party gets much stronger than that, then the party leaders will have to come through on some of their promises, and they don't really want to do that because it's more laborious and riskier than just fighting it out in the 47-53 zone. they get paid no matter what. (Look at the Democrats on healthcare. A bill would be passed by now if Obama and the rest of the leadership wanted one very bad.)
What you'd expect now is for the Republicans to find some tear in the Democratic patchwork and change their message to pry them away and return to the 47-53 area. This kind of demographic research will help them find the tears. The change might take two election cycles.
To a certain extent the ideological Republican Party of the last 17 years or so is an aberration, and there's a chance that the system might be permanently changed. Some of the Republican rank and file are so crazified that they might bolt the party if the leadership makes overtures to some group they're afraid of. This crazification is, in turn, a function of the fact that few voters would really want the what the Republicans were offering if they understood what it was. (For one, they proposed the privatization of Social Security immediately before the stock market lost 45% of its value). So you end up with a core constituency that wants the government to keep its hands off Medicare.
The American political system has powerful self balancing tendencies. The parties are coalitions not ideological constructs, nor emanations of interest groups. Groups, and regions have changed allegiance in the recent past (as Mr. Emerson points out above although crazification is not a word) and they will again in the future. The only safe prediction is that the wheel is still spinning.