I think he was REALLY, REALLY bad. It's not because of what he did, but a combination of what he said and what he did with how the public perceived the issues.
Reagan was supposed to be THE conservative right -> limited government, reduce government, etc. He talked that game and rallied lots of supporters. He went up against the group that used to be the "neo-conservaties" - the liberal right aligned with Nelson Rockefeller and the other welfare state, big-government, internationalists.
But when his actions in office didn't own up to what he was saying, nobody even blinked. People actually believed that Reagan was shrinking government as he expanded it.
Thus, the conservative, small-government wing of the Republican Party quickly became practically indecipherable from the liberal, big-government wing. Non-interventionism vs. interventionism became Republican intervention vs. Democratic intervention. Balanced Budgets became 'harmful' to the economy (which apparently required military-keynsian pump priming). Tax cuts became desirable only as a means to increase government revenue. Sound money was abandoned and inflation was whole-heartedly embraced. Protecting the fruits of your labor became tax evasion. Welfare statism became a debate about tinkering with the details, not about liberty or justice... And I don't think we had one argument about constitutional limitations of power, even after the '79 commitee to determine the constitutionality of emergency war powers.
Basically, the Reagan presidency served to confuse the American public. Corporatism is believed to be capitalism, with its private gains, unregulated fraud, and state cronyism. Once again, the "robber barrons" leaching off of state privilege are called capitalists. We created a partisan issue out of debt. We turned a single economic philosophy that liberty despises (Keynesianism) into slightly varied flavors for each party. We created a partisan issue of non-intervention, with non-intervention seen as complicity with dictators, racism, and genocide, while interventions in the middle eastern world are called a profit-driven "oil empire".
Reagan set the stage for Americans to debate meaningless about the merits of two incredibly flawed big government systems, by aligning his version of big government with all his small government rhetoric.
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