You mis-state the situation.
It would be 8 years of Obama, not 4, if Romney loses.
And it's not guaranteed that it would be 8 years of Romney, if he wins. He could be replaced in 2016 with another Republican.
-PJ
More likely, Romney would be replaced in 2016 with a Democrat. Chuck Schumer is in charge of the Presidential Inaugural festivities in January. Minutes after Romney is sworn in, Schmuckie would run to the cameras and announce "It's Romney's economy now!" All the land mines Obama and the DemocRATs laid would be set to go off, and the media would blame it all on Romney. 2016 would be a Republican blood bath, with the Democrats winning back the House, the Senate, and the Presidency. Hey, Obama could run again! The DemocRATs message leading up to 2016? "WE TOLD YOU SO!"