Arnold Kling:

If I look back over the last thirty years or so, I think that professional economists, like Mankiw, have given good advice. On average, I think that Democratic Presidents have come closer to taking advice, especially advice that might otherwise have been unwelcome.

I am not saying that Carter and Clinton were grade-A economic policymakers, but they left the country with somewhat better policies than they inherited. I think that they differed more on luck than on skill, and if you average the economic statistics of their two Presidencies you get a good indicator of their performance.