As someone who can step out of the partisan box when analyzing a candidate's performance, I'll give Barack Obama a little credit.
Obama is a man of incredible self-control, which has helped him in defending the criticism of his judgment (in fact, his self-control should be emulated by some of his supporting bloggers, but that's neither here nor there). That self-control definitely wins more votes than it loses, especially with the current political circus where proponents on all sides of the ideological divide are angry and bitter and spew likes and baseless ad hominem attacks.
Now, I personally believe that this self-control is partially due to an aloof, arrogant nature where Obama does believe he is better than everyone else in the room, and therefore doesn't need to partake in such practices. I also believe that a lot of his apparent lack of emotional response is increasingly due fatigue from the long campaign, which seems to mute any attempts to show real emotion.
However, no matter the root of this self-control, the bottom line is that it has worked for him.
His inability to show panic when attacked confused many in the McCain campaign. Even when his own advisors showed serious panic, Obama himself never lost his cool. This has allowed him to weather the storms of criticism without appearing disturbed, and allows him to further contrast himself against McCain in terms of age and appearance.
Realistically, though, it's all image. His calm demeanor gives him the image of someone who is not playing politics...although, let's be honest, he's running a campaign that isn't any different from most political campaigns. It's the image that helps him.
Interestingly, that image is what makes him appear post-partisan, despite most of his stances and policies being socialist in nature (c'mon, you can't argue that they aren't, "redistribution of wealth" is a socialist concept which we now know he has admitted to being a goal of his).
That image of unflappability will play well with the voters and on the evening news, but exactly how unflappable Obama will truly be if he is elected President...well, that we won't know unless he is elected and he is faced with true adversity.
So, credit due to Obama...I may think 99% of your solutions to our problems are wrong, but I'll give you credit for your apparent self-control.