I’m sure most of the people who might stumble upon my blog will have played in their youth, at least once, the game dodge-ball. You duck, weave, dodge, and twist to avoid getting it by the ball as it is sadistically hurled by your opponents. I think an argument can be said that the same is sort of true for politics in America.
Now I’m not talking about charges being hurled, that not really what the nimble politician is dodge. Everyone has charges thrown at them and some hit and stick, some hit and bounce off, some miss my a mile and most of the time it doesn’t matter. Your support tends to stay about the same, the partisan stay where they are and the undecided in the middle usually fail to notice.
No, what politicians desperately want to avoid is the negative narrative. A simply handle by which you can describe the politician in question. If it’s negative, and it sticks, that is what the people, including the middle, remember and that will drive, in my opinion only, the sweep of the contest.
It’s not about your positive story and image, every politician ahs a positive story. They are great paragons in defending liberty against all those threats that their opponents either don’t understand or these days you’re more likely to say embody. People are driven towards the positive image as much as they driven away by the negative one. In each campaign someone gets hit with the negative narrative that people start to assume as the truth.

John McCain is an erratic hothead vs Barack Obama is a corrupt neophyte.
John Kerry is weak effeminate man drives by the political winds vs George Bush is an Idiot and puppet.
Al Gore is a boring, officious technocrat vs George W. Bush is reactionary conservative.

Now I am not arguing what is true, but rather what became perceived as true. Each party needs to paint the other with a sticking negative narrative in order to win, and the side that loses is the side that can dodge that storyline thrown from the other side. Once a narrative has hit and starts to grow it spells real trouble because it is very hard to get people to change their minds about storylines. We are story telling animals and we love our myths. I think this is going to be a real problem for the Republicans this cycle.
Romney is tailor made for the Democratic negative narrative. The ‘Etch-a-sketch” gaffe is so damaging because is reinforces the already existing negative narrative that Romney is a phony, and empty suit willing to say anything to win. (A description not terribly untrue for most politicians, but when people believe it then there is trouble.) Combined with Romney’s gaffs on matters of money, you can easily see the negative narrative forming. Romney is a rich, flip-flopping, empty suit trying to buy the presidency.
The Republicans are of course trying to find the right negative narrative to stick to Obama, but they are having a tough time of it. This is why you hear so many wildly negative things about Obama, they’re shot-gunning at the target praying for a hit.