It is the Christian's duty to resist evil. There is no guarantee just when the Tribulation will start. It could begin now, or it could still be sometime in the future. Voting against Obama is part of the fight against evil.

It's not a fight to dethrone the coming Antichrist, or even to overthrow the NWO, as Christians know that only Jesus Himself will be able to put down this great evil. But Christians should still resist the overwhelming evil in the world, and help to reduce its imposed suffering wherever they can.