I believe it was Churchill who said, "Judge a man not by what he says, but by what he does."
There's no better way to choose which politician to vote for. After all, our system virtually forces a candidate who really want to win to parse, massage, mislead, and even outright lie.
If we replace the blather with relevant deeds, the following facts about Obama come into evidence:
The nonpartisan National Journal rates Congress members' voting records on a scale from 0 (most conservative) to 100 (most liberal.) Obama's voting record scored 100. Is this a man likely to be a uniter not a divider? And if you consider yourself a moderate, can you be comfortable with a man whose voting record is maximally liberal?
Obama and his family, including his children, for 20 years attended the church of Rev. Jeremiah Wright. Obama calls him "His spiritual advisor." He donated thousands of dollars to Wright's church. He named him to one of his presidential campaign committees. All these suggest he condones if not embraces the key themes in Wright's sermons. An ABC News review of dozens of Wright's sermons found "repeated denunciations of the U.S.," most memorably saying "God bless America? No. God DAMN America!" Wright also insisted that the U.S. created the AIDS virus to kill Blacks, that the U.S. brought 9/11 on itself, and that anti-Semite Louis Farrakhan is a great man.
Candidly, I do not follow politics closely enough to responsibly and representatively describe the full range of Obama's, Clinton's, McCain's, or Ron Paul's (Yes, he still is running--Here's his Apr. 28 CNN interview) relevant actions. I offer the above two merely because they're the two most glaring examples I've heard of. I don't mean to imply that there might not be equally important facts about the others.)
I invite you to search out the candidates' relevant behaviors, notably their voting records and examples of effective leadership. To those ends, a good place to start is VoteSmart. (When you get there, scroll down.) I'd also just Google the candidates and avoid sites created by the candidates, the parties, or advocacy groups. Instead, read liberal, conservative, and libertarian sites' reporting, not of what the candidates said, but of what they've done.