What these charts show is a clear partisan ideological realignment within one demographic group, white southerners, from 1972-2004, and an otherwise more or less static ideological and partisan electoral makeup of the rest of the nation. More than one third of conservative, white southern Democrats become Republicans, and nearly half of moderate, white southern Democrats not only became Republican, but they also began to self-identify as conservative. Outside of the white south, there was a smaller, though still apparent, shift of conservatives away from the Democratic Party and toward the Republican Party. Those three shifts only one of which was ideological, formed virtually the entire underpinnings of Republican electoral gains in Congress from 1978-2002.
It is important to note that these charts only reflect trends through 2004, and thus do not incorporate the recent favorable shifts for Democrats in terms of partisan self-identification. For example, Harris has shown a five point increase for Democrats relative to Republicans since 2004, and Pew currently shows an even wider gap in favor of Democrats when independents are pushed to make a choice. So, these charts do not reflect just how good the current political situation is for Democrats. Also, there are signs that left-wing ideological labels, especially "progressive," are gaining strength nationwide.
The shift that is taking place now seems to almost be a natural ideological, partisan and even regional backlash to the electoral shift of 1972-2004. The conservative movement basically succeeded in shifting conservatives, especially white southern conservatives, into the Republican Party. Not only did this result in increased gains for Republicans, but it also resulted in moderate and liberal Republicans becoming entirely outmatched for control of the GOP. In the 1970's, there were roughly the same amount of moderate and liberal Republicans as there were conservative Republicans. However, now conservatives outnumber the combined total of moderates and liberal Republicans by a 2-1 margin. In other words, in addition to marginalizing Democratic Party for a number of years, the slow rise to power of the conservative movement marginalized all moderates and liberals relative to the levers of power, not to mention locating the levers of power of the federal government squarely in southern hands (Newt Gingrich, Dick Armey, Tom DeLay, Bill Frist, Trent Lott, George W. Bush, etc).
Given this, the backlash against the Republican coalition that controlled Washington for the early and middle part of this decade was almost inevitably going to be an amalgamated coalition of liberal and moderate non-white southerners. For example, Republicans still control 58.8% of US House seats 77-54, in the eleven states that once made up the Confederacy. However, Democrats control the majority of US house seats outside of the South by an identical margin, 179-125, or 58.9%. The odd symmetry of those numbers stinks of tribalism of the country. It is even tempting to think that the southern-heavy Blue Dogs and DLC often butt heads with the rest of the Democratic Party for the same tribal, regional reasons. This is almost, though certainly not as much, white southern vs. non-white southern as it is conservative vs. non-conservative or Democratic vs. Republican. Republicans have not held a majority of US House or US Senate seats outside of the south this decade, and no Republican has won a majority of the non-southern vote since 1988 (source).
I wonder how long this pattern will continue. The longer the emerging Democratic / progressive coalition is in power, the less unified the rest of the country will be against the soon-to-be-former conservative movement governing coalition. There will eventually come a point where the conservative movement no longer controls the Republican Party to the same extent it does now, and at that point partisanship won't always have the same level of ideological and cultural overtones to it as it does now. However, that will not happen for a while, since the progressive movement still has a long way to go in pushing the Democratic Party to the left, much less assisting in a DLC-style reorganization of the Republican Party.
