Perhaps the biggest surprise of last Tuesday was Indiana's move to the Democratic column. Not since LBJ's landslide 1964 victory had the Hoosier State gone blue. In looking at the returns we see that Obama was able to drastically improve upon the performance of past Democratic candidates. His vote share grew in every county versus Kerry's 2004 performance, as the map at left shows (for some coverage from the Indianapolis Star, see here). He was able to win 12 more counties than Kerry (15 total), and his performance in Marion County (Indianapolis) allowed him to generate a huge number of votes to help tilt the state. In 2004, Kerry beat Bush in Marion County by 2% (6,000 votes). This year, Obama beat McCain there by 28% (107,000 votes)!
As during the Democratic primary, Lake County was also crucial to Obama's success. Essentially a part of the Chicago metropolitan area, Lake County's Democratic share increased 6% over 2004 and gave Obama a 71,000 vote margin.
You might also look at the Indiana college population for part of this year's margin. Monroe County (Bloomington) is the home of Indiana University. In 2004, Kerry won the county by 8%. This year, Obama's margin was 32% (20,000 vote margin). Tippecanoe County (West Lafayette) in north east Indiana is home to Purdue. Whereas Bush won Tippecanoe by 20% in '04, Obama switched the county, winning it by 12% (8,000 vote margin). Finally, the University of Notre Dame resides in St. Joseph's County (South Bend). Here we saw another switch--whereas Bush won the county by 2% in '04, Obama enjoyed a 17% win (20,000 vote margin) this year.
For all the details on Indiana politics, see Howeypolitics.com.