For what it's worth, it seems to me that the idea of moral obligation is to do what is right even when it is not advantageous. I fully understand the math of the state of this election, but the lesser of two evils is still an evil.
As an aside, I'm not bent on calling either major candidate an evil. There are things about both I like, and there are things about both I can't stand. Then there are third parties that I am much more on board with than either.
But here's another thing about numbers. So long as the mentality of "if you're not A, then you're really supporting B" is perpetuated, we'll never have viable third parties. In the short term, voting Johnson instead of Romney means one less vote toward the major possibility of having someone other than Obama in office, but it may have long-term gains. Say 2% of voters this election vote Libertarian (or Green or Justice or anything else). That's 2% that Republican and Democrat are both missing. What if 2% this election becomes 4% the next and so on? Even if it's one vote at a time, the only way a viable multi-party election will come about is if people start worrying more about supporting what is best rather than what is thought to be less bad.
To continually choose the lesser of two evils only slows the rate of descent into evil. [Edited] I see the merit to such a pragmatic approach now. Still, like with the example of the Mexico City Policy, one candidate from one party can do a certain good that the next president from the other party can just as soon undo. Does picking Republic now to only have the next Democrat undo it (or vice versa) reap longterm rewards, or is it possible that enduring a greater evil for a while to support a greater good in the future could be the better option?
And, as another aside, to say "a vote for a third party is a vote for Obama" assumes that the vote would otherwise go to Romney. Does the same remain true if someone who would typically vote Democrat votes for Jill Stein, or is that a vote for Romney?
The job of the American people is to support what they think is in the best interest of the country last I checked. Call it idealism. Call it naive. But I still cling to the American dream and American values of no-compromises in truth, justice, and the common good. Yes, it's true, elections come down to votes, but politics and voting (and making morally-sound decisions in general) need to be more than just numbers games.
My $0.02.
Edit: Didn't read the article yet, but these thoughts have been running through my head for a while now, and I couldn't hold them in anymore.

Gonna read it now, though.
Edit 2: Okeydokey. Read the article. Really liked it. Really glad I did. Thanks.

He's got some great points. I have a hard time disagreeing with his reasoning. I think there's definite merit to saying that the lesser of two evils may be still evil... yet it is still less evil.
But I still ultimately stick to my idealism. It's worth clinging to for me, but I do get the more pragmatic option and understand the math behind it. And if you (applying to anyone) feel that it is better to vote for the lesser of two evils in voting than choose a more ideal third option that has practically no chance of winning, more power to you.
