Sarah Palin called this the "election of our lifetime", although that term might come in to play again in 2012 should she decide to run. However, with the nation in the shape it's in right now, change has to be made.
Obama thinks that the democrats can make that change, and wants some more time to get the change that he promised during his campaign. According to Obama, a GOP lead in the government would undo all the 'progress' that has been made.
Below see a video of President Obama campaigning for the Minnesota Democrats.