The economic disaster that has been Obama and his failure to lead and unite has doomed his presidency.
The most likely thing to doom Obama is an economic catastrophe locally. A foreign economic catastrophe won't be factored in so much by the US electorate unless it immediately affects the US and in that case it becomes a local catastrophe. Of course with such a highly interdependent economy that could happen. A security crisis and natural disaster are more likely to cause a rally around the Flag reaction that will benefit the incumbent, with the exception that it is obviously the fault of the Admin. and or the immediate response is bungled and I don't think that will happen. Further if Romney tries to capitalize on a disaster of that nature right away it will look very bad for Romney. It is one thing to politicize a response a year later as was done with Katrina and another to do it the day after the disaster. Other than those some sort of big scandal or epic meltdown by Obama would be the only other things that could guarantee handing the White House to Romney. Obama seems too smart though to let something like that happen to him now. That said there is a still a long time in political time between now and the election and something as simple as an uptick in unemployment could cause Obama to lose.
Keep in mind though that Romney was attacked for his wealth, and how he got it, first by other Republicans in this year and the 2008 primaries so this line of attack wasn't pioneered by the Obama campaign.
I'd say it's because Nixon was totally unprepared for a new medium, and the breed of politicians today are alive because of how much better they compete in it. I mean if were going to compare hindsight observations, I'd gave no idea what extent if John good hair, good smile Edwards character flaws would be by his appearances alone. And i must say that despite that performance, Nixon managed to rebound in subsequent TV appearances, so the stigma of his trustworthiness didn't become apparent until way way after.
If unemployment gets higher he loses. If there's a big domestic terrorist strike (on a 9/11 magnitude) and Romney can paint that, along with Libya and Egypt, as signs that he's soft on defense and "apologizes."
