And just how good of a politician WAS Clinton?

Perhaps the reason for Clinton's reversion is that the old formula didn't actually work that well. As Auren Hoffman points out Clinton actually wasn't such a successful politician afterall. Can it be that while triangulation was a successful strategy for him personally it wasn't so great for the party? Excerpt:

When Clinton assumed the presidency in 1993 the Democrats controlled the executive branch, the senate, the house, the majority of the governorships, the majority of the state legislatures, and a majority of all elected officials nationwide.

When Clinton left office in 2001 the democrats had lost control of everything. They lost the presidency, the senate, the house, a majority of the governorships, a majority of the state legislatures, and a majority of all elected officials nationwide. In fact, Clinton presided over a dominant resurgence of the Republican Party (which is now in its tenth year).