Not So Crimson Tide
In undergrad, I vaguely remember reading about some theory on presidencies. I don't remember the details, but basically it claimed that there were four kinds of presidencies throughout American history.
1. Presidents who usher in new eras. Not era as in time, but as in political ideology (Lincoln, Teddy?, FDR, Reagan).The starking feature of a no. 4 president is low approval ratings. Well Newsweek has released a poll revealing that Bush's approval ratings are at 28%. The lowest number since Carter (who was also at 28). Think about that.
2. Presidents who are elected in their own era. (LBJ, Harding, Coolidge, etc.)
3. Presidents who are elected in the wrong era. These are the ones who tend to get impeached because the political tide is against them. (A. Johnson, Nixon, Clinton).
4. Presidents who are the last of their era. They immediately precede no. 1 presidents. (Carter, Hoover, etc.)