Beyond the policies, the lies, the impact on the Supreme Court, the devastation to domestic needs, etcetera ad infinitum if Romney wins, there are two other important reasons to vote for Barack Obama.
One, to which I've referred before, is that to vote for Mitt Romney is to empower the literally insane people in his party serving in Congress, who believe climate change is a hoax, that science is the work of the devil, that the biblical law supersedes the Constitution of the United States, that only white Christians deserve to be here. (Along with their womenfolk chattel, that is.) It's to legitimize lying over truth, ignorance over education, denial over reality.
But the other is the better one: I really really want to see what the RWS™ and crazies say when it does NOT come to pass that Obama will confiscate their guns, ban the bible, facilitate a Muslim/Sharia takeover, declare martial law, round up Republicans and put them in concentration camps, turn the US over to the UN, and/or implant RFID chips in every citizen. And countless other dire warnings and crackpot conspiracies that motivate so many of the teabagger mentality. (What he will do, mark my words, is piss off some liberals by addressing Social Security and Medicare in ways they might not like. But, unlike Mitt Romney's vaporous and regressive and mathematically impossible plans, it'll be to make them financially solvent for those who need them most.)