As a general rule of thumb, the more awful a president was, the better "history" treats him, and vice versa.
Not necessarily - the pre-Civil War Presidents have not be rehabilitated, nor do some Presidents like Arthur fully get their due.
Presidents, like other political figures, have a tendency to be forgotten once enough time has passed. Some big names like Washington & Lincoln are clearly remembered by everybody, but others like Fillmore & Arthur are largely unknown to the general public, & as a consequence now are viewed in a fairly neutral light (neutral in the sense of lacking any strong impressions of them).
