4. The Republicans are weak and divided.
You can't beat something with nothing. That old saw in politics wins out most every time. The Republican Party has never gotten over its love affair with Reagan. Look at the parade of Republican hopefuls who rose and fell during primary season. Had Reagan been around, he'd have been frustrated with the divisions in Republican ranks. And the Gipper might have described the primaries as an audition in which the last guy standing got the part only because the producers were exhausted and needed to get the play into rehearsals before the opening.
I know the main counterpoint: Republicans will come together because they need to defeat Obama. But the gaps between the Republican base and the centrists are huge; the obsession with social issues risks alienating independents; there are real doubts that Romney is conservative enough; and there's not much enthusiasm for his stiff style on the campaign trail. All this is creating real trouble for a party that seems to have lost its way. Add to that Republican difficulties in making inroads with women and Hispanics, and you might conclude that the election is Obama's to lose.