I have to disagree with your contention, Bruce, that supply-siders are a dying wing of the Republican Party. If anything, they're now all supply-siders to the point that it's not even a point of self-identification anymore. Just look at this morning's Republican debate: Not one of the candidates said they would raise taxes to repair roads and bridges. Rudy Giuliani and Mitt Romney started saying they'd cut taxes to raise the government revenues.
If that's not a consensus of Lafferism, I don't know what is. Republicans have really bought into this little fairy tale, that we are forever and always on the far side of the hypothetical curve, and it seems like nothing can convince them otherwise no matter how big the national debt gets along the way.
And furthermore, what exactly does the Laffer Curve look like? Can anybody produce one, based on actual economic statistics over a long period of time? As it is, the GOP has made a religion out of the fiscal solutions of 1981, and the imaginary curve just keeps getting pushed further and further back to justify more tax cuts. Forget about the religion and the articles of faith, I want to see some evidence.
Which brings me to these questions: under what circumstances would our modern Republicans approve of tax increases? Is there any such scenario where a pressing need would justify a raise in the marginal tax rates? Or is the solution to every last problem a tax cut, resulting in a quasi-Keynesian stimulus and debt accrual, all of which is then hailed as a victory of small-government conservatism? How will those Treasury Bills finally get paid?