Barack Obama is in trouble with American voters, but his re-election might well depend on the identity of his GOP challenger. Establishment Republicans and other political pros think Mitt Romney is the most likely candidate to unseat President Obama a year from now. But the Iowa caucuses could change things, as they did four years ago, and they're less than two months away. Will Mitt Romney go all out despite being clobbered in Iowa four years ago? Will a fourth woman damage Herman Cain with sexual harassment charges? Can Rick Perry spend his way out of a collapse in the public opinion polls? We look at some potential scenarios for Iowa and 11 other swing states, which could ultimately decide if there's going to be a change in the White House.