Time never cares just what we do/it just sits on a star and gazes down...
And shores up the reputations of American Presidents. Parapundit's Randall Parker posted recently on Bush's honored status as runner-up for the most disapproved of President in US history. It's hard to argue with that. In his defense, though, time tends to improve the standing of former Presidents in the eyes of the public.
Using an 'approval ratio', computed by simply dividing the percentage of the public that approves of a President by the percentage that disapproves of him (taken from this Rasmussen report), and the number of years since he left office, I ran a regression to see how the two correlate (data via Swivel here). The relationship is a statistically significant but modest .39.
This isn't a satisfactory gauge, however, as there are several Presidents who have mostly flat ratios constructed by the opinions of a small minority of the public. For example, the arch lameduck John Tyler was unknown to three-quarters of those surveyed, even though he provided the executive impetus for us to take Texas. By contrast, all of the participants had something to say about the second Bush. The period from the second Adams to Lincoln is chalk full of unknowns, as is the period from Lincoln to Teddy.
This is due largely to the way contemporary American history is taught. The Founding Fathers created an egalitarian democratic republic that, despite these few brave deists, was mired in racism and bigotry until Abraham Lincoln came to emancipate the country from itself. That was followed by evil corporations and the barons who controlled them, until the Bully came and busted them up. A period of steady governmental improvement (accretion) has since followed.
Removing from consideration all those Presidents who were unknown by at least one-third of the survey participants yields a much stronger correlation of .57. Those in recent memory fared quite poorly, even as the US won the Cold War and experienced stellar economic growth. The Gipper, who was voted the greatest American of all time in an AOL/Discover Channel poll, was outdone by each of the founders save for James Monroe (himself a sort of honorary founder who didn't actually sign the Declaration).
The tendency to glorify the accomplishments of past leaders shows up even in contemporary partisan politics. In the risible Presidential IQ hoax that surfaced in 2001, the fake ranking of vapid Republican Presidents is almost perfectly chronological, with Dubya as the dumbest, followed by his dad, then Reagan, then Ford, with only Eisenhower and Nixon swapped. This variation is probably because Nixon was 'crooked'--like in the Simpsons, the media can portray Republicans in one of three ways: As prudishly ignorant religious folks (Ned Flanders), as chauvinistic lazy slobs (Homer Simpson), or as intelligent but greedy, heartless miscreants (Mr. Burns).
Despite squandering US international clout, blood, and treasure in Iraq, expanding the size of the federal government at a rate greater than his predecessor, and making perennial attempts to force onto the American citizenry a disastrous amnesty for a growing illegal Hispanic underclass, Bush 43 will likely see his reputation ameliorated with time.
When Nixon left office, his approval rating was a dismal 24%, but today it sits at 32%. That suggests an improvement with time for the current President, but it's contingent upon how low he can go while he's still in office. We still have almost a year-and-a-half for him to dig a hole even bigger than the one dug by he who went to China.