Brad DeLong says:
…nobody who has not served a full term as a state governor or managed a similarly large organization should be supported in any presidential run. FDR and DDE are certainly the class acts of the twentieth century.
…there’s not much of a difference, but what differences there are tend to suggest that legislators, and not governors, have a small advantage.
Some more elaborated statistical analysis suggest, actually, that prior experiences of any kind have little to do with presidential greatness. Or so argues John Balz in a recently published paper (gated). We discussed an earlier version of this paper here, and there is an ungated pdf at that link. From the abstract:
Overall, there is no evidence that political experience improves the likelihood of strong presidential performance, and even some weak evidence that political experience in certain political positions, most notably mayor and member of Congress, leads to poorer performance. In the end, great presidents are not great simply because they have spent their lives in politics and learned important lessons.
Here are some details:
Time spent as a mayor, a member of Congress, a state administrator, a federal judge or attorney, or a soldier leads to a lower ranking….The largest of these effects is for mayoral service, with each year in office lowering one’s ranking by more than three spots. Since only three mayors ever became president, these findings should be interpreted cautiously.
On average, experience as a diplomat, soldier, and a member of the private sector also decreases a president’s ranking, although the effect is not robust to 95% credible intervals. Experience as a governor, state legislator, state administrator, and general improves ranking, on average, but these effects are also not robust to 95% credible intervals. The largest of these effects is for general, which might be driven by the top-10 rankings of three presidents with long careers as military leaders: George Washington, Andrew Jackson, and Dwight Eisenhower. It should be remembered that the president with the most experience as a general, Zachary Taylor, was also one of the country’s worst presidents.