For thirty years, the Republicans have implemented their theories into policy. They wanted income tax cuts. They got them. The top income tax rate is half today of what it was 32 years ago. They wanted corporate tax cuts. They got them (not to mention more corporate loopholes than can be mentioned in this response). The top corporate tax rate is 11 points lower today than it was 32 years ago, and 17 points lower than it was in the 1950s. They wanted capital gains tax cuts. They've had them. They haven't been this low since the Great Depression. They wanted deregulation. They've had it in spades. From the Enron loophole to the unregulated gambling in all things derivative, to ending the distinction between investment and commercial banks, to allowing more risk throughout the banking industry.
Their policies have failed by every measurement. They promised more growth, we got less. They promised more tax revenue, we got less and it grows less now than before. They promised market stability and self regulation and sophisticated markets. We got the worst financial crisis since the Great Depression, and massive increases in income disparity, plus our massive increase in debt...
[Now] they want more, and they want the middle class to both blame themselves for wanting too much government, and to pay for it with cuts to public schools, infrastructure, and Social Security and Medicare.
---"Chris" commenting on this Krugman piece
Update: Commenter Russ Hunt, at the link: Their policies have failed by your measurements and mine, but perhaps not by theirs. Consider what they've achieved.