How Did Mark Kirk Win Obama's Former Senate Seat?

How was Illinois GOP Congressman Mark Kirk able to win away President Obama's former Senate seat from Democrat Alexi Giannoulias? 

Political analysts said it was "crucial" for the President's party to win.  "The national political parties were very involved this race.  It was one of the marquis races.  There was a lot of symbolism to it." says Tom Bevin of Real Clear Politics

Obama even came to Chicago to campaign for Giannoulias.  It was a very tight race all along.

At any given point it looked like one or the other might win.  So how did Kirk come out victorious?  "Our victory...had many mothers and fathers" Kirk's people said, in one of his final campaign emails sent to supporters. 

Here are the numbers, broken down by Kirk's campaign:

Votes earned: 1,765,594,  Volunteer phone calls made: 4,115,347

Volunteer door knocks made: 214,275,  Yard signs deployed: 27,898

Money Raised: $14,115,907.48   Events Held: 777   Communities Visited: 152

TV Ads Broadcast: 20      Radio Ads Broadcast: 7

And then Kirk's people added this little quip "Cost of Thoughtful, Independent Leadership for Illinois: Priceless"