The Washington Post website has an interactive "choose your candidate" tool that purports to show you which candidate you should be supporting, based on their public statements on a variety of issues, and how important you say these issues are. I spent some time playing with it, and it mostly demonstrated to me how close the Democratic candidates are on most of the issues that I care about. If you can parse the differences between what they're all saying on Social Security or immigration, you're doing better than I am. And while the tool lets you say how much you care about the issue in general, it doesn't have any way for you to indicate how much you care about the differences in the candidates' positions. I think I gave up on it about halfway through, when it was saying I should be supporting Chris Dodd.
Precisely because the candidates are so close together on policy, the areas where they disagree, even a little, are getting a lot of attention, perhaps excessive. One of the areas where some differences have shown up is on health care. Kucinich is the only one standing up for a true single payor system, while Obama has criticized Edwards and Clinton for requiring everyone to get health insurance. He's dead wrong on this -- both because you really do need to get everyone into the insurance pool in order to avoid people freeloading until they actually get sick, and because the attack on "mandates" is likely to come back and haunt him if he actually gets elected. (I don't have the energy to go hunting for a full set of links right now, but this has been exhaustively discussed in the wonkosphere. )
So, on one of the few areas of substantive difference, I think Obama's wrong. But I still think he's my pick. I'm embarrassed by that. I'm a self-proclaimed policy wonk. But he makes me want to believe.
On a related topic, this week you'll see an ad in my sidebar from the fine folks at One.org, who have asked all the candidates about what they'd do to fight international poverty and disease. Spotlight on Poverty and Opportunity is a similar exercise focused on domestic poverty. Check them both out.