An emotion not unlike depression brought on by the realization that you voted for Obama due to white guilt, and now you're going to get screwed because you're not "ethnic enough" for change.
Larry the anglo-american construction worker finds out his firm is letting him go for more "ethnic" workers as part of a bailout package his employer and union will be receiving. It doesn't matter that the people being hired are underqualified, they're the right color. He's experiencing an "O-bummer".
1) Refers to negative events, actions, or reactions that are specific to the Obama administration.
2) any event which results in a loss of hope or a general "no we can't" attitude.
Having 3 of Obama's choices for his cabinet drop out is a real obummer this early on for his administration.