Nate points out that Obama’s approval rating at the start of his presidency is higher than anyone since John Kennedy, and he writes, “In comparison with Ronald Reagan, however, Obama’s approval is quite a bit more impressive. Indeed, it is hard to mount a credible argument that Reagan began his term with more political capital than Obama.”

I recall reading that Reagan’s popularity jumped after his attempted assassination two months into his presidency. (See here for some graphs.) So I suspect that the impression of Reagan being initially popular comes from that point, not from January 20.

P.S. Recall that Reagan, like Roosevelt, was a statistician.