"As people like me, for instance, get more and more left-wing in our advocacy, the moderate conservatives respond by advocating extremely conservative positions."

Perceptive. So if an extremist feels the center is his greatest obstacle to power, it is in his interest to polarize the dialogue and essentially undercut the moderates, leaving the bulk of the spectrum to either join him or his extreme opposition. If the extreme opposition is rejected by the center for historical or practical reasons, that means the bulk of the middle will go to his side.

If this happens deliberately, i.e., it is a planned as opposed to a natural evolution, it is because one side felt that it had an edge and could win it all by forcing the center to split. It happened in Russia and in Germany that way after WWI, where in both cases a vast centrist majority had to be divided in order for the extremists to meet on the borderline and duke it out.

Applying this paradigm to the USA and to my own point of view, this is what the extreme right is trying to accomplish in this country. The extreme left is so disorganized, fractious, bizarre and incoherent that the moderate left and center is reluctant to join it in order to oppose the right. The extreme right, on the other hand, organized and disciplined, is passing itself off as the middle of the road and is actively courting the center and moderate right forcing the left to either follow, or adopt increasinly strident far-left attitudes.

That's a depressing scenario, Bowz. Especially since everyone sees themselves as "moderate" or "centrist". No one describes himself as "extremist", not even to himself. The only way around this impasse is to cultivate those on the other side and try to find common ground, compromise and tolerance, and to reject those who insist on extremism of any sort. But of course, that is pollyanna-ish appeasement, isn't it?

Blessed are the peacemakers...