Conventional wisdom holds that second presidential terms tend to be somehow fatally cursed—Eisenhower and the U-2; Nixon and Watergate; Reagan and Iran-contra; Clinton and impeachment; George W. Bush and Iraq and the financial collapse. The implication is clear for a newly re-elected president like Barack Obama: be careful what you wish for.

As usual, though, the conventional wisdom obscures as much as it captures. Second terms are perilous, but so are first terms: politics are always perilous. Looking ahead (itself perilous!) it’s likely that Obama, if he is like his predecessors, will find himself able to do one or two big things domestically and freer than he has been to operate globally as he wishes....