In The New York Times Today is this interesting lament by Steven Heller about the clichéd campaign posters. The two posters above are among the exemplars that Heller offers of graphics that avoid banal flag waving (he offers a couple more that I find significantly less compelling); and the essay itself is inspired by this poster.
Here is another recent, and unfortunately unsuccessful, campaign poster that I have mentioned here several times before.
The question is whether such graphics have much effect on perceptions or attention. I do know that the ones I like (nos. 1,2,4) are dissenting and oppositional, while the Obama poster is not just "affirmative" but suspiciously diffuse (as are the others that Heller offers as examples - in my view they each fall flat). I know what the other three are after, This mantra of hope makes me want to put my hand over my wallet to make sure my pocket is not being picked.