My conclusion is that this characterization is a bit misleading. The apparent underperformance of Obama can partially be explained by structural factors, most notably the fact that the Democrats have a wider, more diverse coalition than the Republicans. It is therefore more difficult for any one Democratic nominee to please all his party's constituents.
But also, Obama has heretofore been unable to brand John McCain as a Generic Republican, as McCain is regarded by much of the electorate as a moderate. In terms of their distance from the median voter, then, Obama v. McCain is a much fairer fight than would be indicated by their respective party affiliations:
In terms of party principles, the Democrats have already won the election. The party's liberal base didn't have to compromise on its candidate, whereas a substantial number of conservative Republicans did.In a sense, I think the media's Obamacentrism has confused it (the campaign coverage has certainly been Obamacentric -- though by no means always Obamaphilic). If Obama is underperforming a Generic Democrat, that is presumed to reflect some or another weakness of Obama's. But it could just as easily reflect some or another strength of John McCain's -- such as his perceived moderation. Since Obama was polling ahead of non-McCain Republicans by blowout margins, I would argue that the latter is more likely.
But the Republicans seem wise to have compromised, because polling showed that Obama was headed for a landslide victory if his opponent was an identifiably right-wing candidate.
According to polling averages compiled by the website RealClearPolitics, at the time they discontinued their respective presidential bids, Fred Thompson trailed Obama by 12 percentage points, Mitt Romney was behind by 15 and Mike Huckabee by 17. For that matter, a recent poll from Rasmussen Reports showed Obama leading President Bush by 20 percentage points in a hypothetical matchup.
McCain has managed to retain his reputation as a moderate and thereby avoid the fate of his conservative former rivals of falling far behind Obama. And so Democrats will aim to undermine McCain's perceived moderation -- by possibly highlighting his rightward shifts during the Republican primaries and by attempting to tie him to Bush. The problem for Obama is not so much that he's underperforming a generic Democrat. It's that he hasn't yet been able to re-brand McCain as a typically conservative Republican.
To make this something of an omnibus thread for media hits, you can listen to the audio of my interview last week with WNYC's Brian Lehrer here. And I'm cited in an article by The Politico's David Mark on electoral college ties here.