I'm not at all sure that any of the four candidates (Obama, Biden, McCain or Palin) are qualified or ready to do this. The three senators haven't got any executive experience; they haven't even managed anything. The governor hasn't had enough executive experience to be much better (and doesn't have a good enough grasp of the facts and issues).
But during the last week, I think it has become clear that Obama is far, far more equipped than McCain to deal with the problems at hand. McCain's response to the financial crisis this week was shameful, calling on the firing of the chair of the SEC, pointing fingers, pandering and sounding hysterical. Obama was calm, reassuring; he waited till the Bush government had spoken; he said his team was working on a plan that would be released soon.
Furthermore, the most important ideological difference between McCain and Obama is that of "no more big government" and "free markets" vs accountability, transparency and effective regulations. It is clearly the time to stop the process of deregulation and start rebuilding safeguards. Even Wall Street admits that financial regulations are obsolete and need to be completely overhauled. Similar recent problems have shown the need for stronger regulations on corporations, consumer products, the environment, food safety, elections, and other areas. Having a president who is ideologically opposed to regulation is just not what is needed right now.
I like McCain and I wish him a happy retirement. But it is clear that Obama is by far the better choice for president.