If Obama wins, he will be the first President to be re-elected with a reduced...

[Mr. Morden]

I don't think any president has ever won a *second* term with a reduced popular vote and electoral vote %age from his first election (as you mention, FDR did that for his 3rd term, but not his 2nd).  It's happened where they'll win with a reduced popular vote but increased electoral vote and vice versa, but whenever both go down, then the incumbent loses.  So if both go down for Obama and he still wins, it would be a first.

[Mr. Morden]

I don't think any president has ever won a *second* term with a reduced popular vote and electoral vote %age from his first election (as you mention, FDR did that for his 3rd term, but not his 2nd).  It's happened where they'll win with a reduced popular vote but increased electoral vote and vice versa, but whenever both go down, then the incumbent loses.  So if both go down for Obama and he still wins, it would be a first.

I think Wilson did...

No, his popular vote %age went up from 1912 to 1916.  Of course, there was the special circumstance of having such a strong 3rd party candidate in 1912, but it still doesn't quite meet the criteria being described here.

[Mr. Morden]

In fact, if you ignore the electoral college and consider just the popular vote, then the last incumbent president to win a second term with a reduced popular vote %age from his first victory was Andrew Jackson in 1832.  And I guess he was the only one to do it, since there was no popular vote before the 1820s.