Have the Political Parties Changed That Much?

There's a discussion of the claim that the major parties have switched positions over the past century at Statistical Modeling, Causal Inference, and Social Science (seen via God Plays Dice). I don't see how there has been that much of a change.

As fas as I can tell, the Republicans, from the start and continuing to the present, have been based on the following two principles:

1. Big business is America's persecuted minority and deserves an affirmative action program. (The first makes some sense, but I think the second part is going too far.)

2. Single-issue voters should always be taken seriously if they don't interfere too much with big business. This applied to anti-slavery voters, anti-alcohol voters, anti-abortion voters, etc. Sometimes this makes sense and sometimes it doesn't.

Ever few decades, the Republicans decide that there are more voters on one side of a single issue than the other and swing from one extreme to the other. For example, John McCain appears to be betting that there are more open-borders single-issue voters than closed-borders voters.

On the other side, the Democrats have always been about identity politics. They started out as the rural white identity-politics party and have gone through several changes in their list of favored ethnic groups since then.