There are three incumbents on that list who lost re-election. Safire's hyperbole notwithstanding, none were remotely close to Obama in political talent. Two of the presidents lost to opponents who were way more talented campaigners, the other had never won a race bigger than a CD. And none were dealing with a conspicuously obstructionist congress. This doesn't mean he can't lose or his approval rating isn't a factor. But it does mean we should hesitate to extrapolate x is the approval rating cut-off from that very limited data from dissimilar circumstances.
Is Obama more of a political talent than Ford, Carter or Bush 1? Yeah, almost certainly (not that this is a high bar to clear). But again, at the start of the '92 election, Bush was not thought of as a political no-talent but as a guy who decimated Dukakis after trailing by 17 points. Carter was perceived as an ex-peanut farmer who became president kinda miraculously after serving a single gubernatorial term. "Safire's hyperbole" was not his own view, but a recitation of the CW about Carter -
this Guardian postmortem on the campaign describes "electioneering" as the "one skill" Carter "was reputed to have." Basically, anyone talented enough to get elected president is going to be thought of as a highly talented campaigner. Obama's really not unique in that regard.
In point of fact, Ford and Bush did have hostile opposition congresses, which they tried to run against, Truman-style, before moving on to other strategies (check their convention acceptance speeches).