It's really easy actually. He has not represented my views sufficiently to have earned my vote. If the Forvm faithful recall, I believe he should be impeached for failing to prosecute credible allegations of torture that occurred in the Bush administration. Our treaty obligations require this, and he has chosen to ignore them.
For the record, I have been eligible to vote in 2 Presidential elections. In 2004, I voted for Michael Badnarik (L), and in 2008 I voted for Ralph Nader (I). I am currently undecided for 2012.
My friends here (and a good deal of the people I know) tell me, essentially, that a vote for anyone but Obama is a vote for Romney. I also get "but you live in OHIO! Maybe if you lived in New York, sure, but OHIO!". I've heard it for years. Here's my defense of my minorpartyphilia.
1) Voting for the lesser of two evils is still voting for evil.
Is Obama better than Romney? Yes. Will Romney or Obama win the election? Yes. Do either of these matter? No. Voting is quite possibly the most useless thing someone can do to change government policy (more on that later). Voting is properly understood as a declaration of principles and preferences. I'm a principled person and if someone doesn't earn my vote, they don't get it. It's as simple as that. If it came down to me and my vote determined if Obama won the election, I still wouldn't vote for Obama. The consequences of my vote are not important. If Romney wins and thousands of people die because of the PPACA repeal that is sure to ensue, that is still not my fault. That's Romney's fault for signing the bill, Congress's fault for passing it, and the fault of all the people who voted for Romney.
2) A single vote doesn't (usually) matter
A person's vote is only useful for changing the outcome of an election if the winning candidate wins by exactly one vote. I don't believe this has ever happened in a federal election (the closest I can find is the 1974 US Senate election for New Hampshire). If you're worried about changing the outcome of an election, you should be dealing with GOTV operations, phone banking, etc. in states that are in play. Doing that can help swing an election. My vote doesn't affect anyone else's vote. If I vote for Ralph Nader, that adds exactly one vote to Ralph Nader's totals. It does not swing multiple votes to his column.
Why usually? In local races, it could come down to one vote. I've seen Sunday Sales here*** go down to a single vote or tie in several cases. Pragmatism might be advisable at such a low level.
This is also why I don't mind to "waste" my vote by voting for someone who "can't win". My vote isn't that valuable to begin with, so it isn't much of a waste. I wonder what the adherents to this belief that voting for a minor party/independent candidate is a waste counsel Utah Democrats (or Republicans for that matter) to do. Obama can't win Utah. It won't happen. Romney can't lose and will probably set a record for largest margin of victory in a particular state. In the 2008 primaries he received 90% of the vote in Utah. Why would anyone hold their nose and vote for either over someone like Virgil Goode, Gary Johnson, or Jill Stein if those people better represent their views? Based on the fact that Obama can't win, the only logical conclusion to draw is that one must vote for Romney. The reverse is true in Vermont.
***In Ohio, if a business wants to sell alcohol on a Sunday, the precinct in which the business is located votes whether or not to allow it. Precincts are usually around 300-700 people, and with turnout rates in the 10% range for off-year primaries, one vote can really make a difference.
3) The major parties are downright hostile to the idea of free and fair elections.
Ballot access laws among the several states are largely arbitrary and discriminatory. The laws, even when followed, are unequally applied. In 2008, all parties in Ohio had to provide their nominees for President on the same date in August. In 2012, the legislature passed a bill explicitly giving parties with over 20% of the vote in the last election a few extra weeks. Why? The last convention this year isn't until then. Why not give everyone extra time? Because screw them, that's why. They're the competition by God! Were you aware that in Texas, both John McCain and Barack Obama missed the deadline to be placed on the ballot? They did, but the SoS put them on the ballot anyway and when Bob Barr filed suit, the state supreme court denied their petition.
What does this have to do with Obama? He's a member of a major party, and I haven't heard him say word one on equal ballot access.
As I said, at the moment I'm undecided. It'll probably be Rocky Anderson or Jill Stein, but Gary Johnson might make his way in there. And of course, it depends who is on my ballot (although that'd be because of inept campaigns as Ohio's ballot access law is quite easy at the moment -- namely we don't have a constitutional way to qualify a new party and the state legislature hasn't repaired this defect in four years).
If anyone wants to convince me to vote for Obama on his merits, I'm listening.