Bush’s low approval ratings are an illustration. Some experienced GOP campaign strategists believe that there is virtually no chance that a Republican can succeed Bush if his approval ratings remain mired in the 30s. The Democratic strategy of investigating administration scandals and policy blunders is calculated to achieve exactly that goal — and the burgeoning controversy over the firings of eight U.S. attorneys has given Democrats in Congress yet another inviting target. ~The Politico

Come to think of it, has the outgoing President’s party ever won the next election when he has approval ratings below 40%?  I don’t think modern approval rating-taking existed before Truman, but we can also see from the fairly lopsided Harding victory in 1920 that unpopular Presidents consistently drag down their succeeding nominees down to defeat.  Relatively more popular Presidents, such as T.R., Coolidge and Reagan, have been able to hand over control to someone from their own party (though not always necessarily their Vice President), which also makes Gore’s inability to match these examples particularly bad. 

All this seems obvious enough, but for some reason much of the commentary on ‘08 has been treating the election as if we still lived in the 50-50 nation and it’s anybody’s guess which way the election will go.  All generic polls and common sense tell us that the Democrats will once again do pretty well, barring some catastrophic failure or scandal on their side.  Even if we were not still in Iraq, it seems probable that Mr. Bush’s low approval ratings and the GOP’s generally poor reputation these days will make the GOP nominee this time around a dead man campaigning.   

That once again makes 1920 the more appropriate model for understanding what is likely to happen next year (with all of the obvious caveats about significantly different electorates, circumstances and issues taken into account, lest I be accused of young blogger naivete).  Another comparison would be 1952, which technically included Truman early on in the election but was effectively an election without an incumbent from either party.  In terms of the final margin of victory, 1952 is probably the better comparison than 1920, which saw a massive blowout that does seem unlikely given recent voting patterns.