The top three vote getters for President in November of 2012 will be: Barak Obama, Mitt Romney, and Gary Johnson. I think that there is a legitimate argument for voting for each one of them.
Vote for Obama: If you think that this country is going to go the way of economic collapse, then vote for Obama. Let's get it over with. Dragging it out will only prolong the pain. (Some nicer sounding, and unconvincing reasons here.)
Vote for Romney: He's not Obama. (Although his positions on the most important issues are the same.)
Vote for Johnson: If you think that this country has a chance to return to its former greatness, then vote for Johnson. Unlike certain republican vice presidential nominees, he has a plan to balance the budget next year, not sorta balance it 10 years from now. He's also actually in favor of ending undeclared wars, and ending the government's spying on its own citizens.