I don't think he has been that polarizing. Great presidents seemed to be defined by trying times (Washington & building a nation, Lincoln & the Civil War, FDR & WWII, JFK & the Cold War, etc).

*KnocksOnWood But I don't think Obama has experienced as tragic yet. I think 9/11 was the moment where Bush could have been up there with the greats, but he failed. I think Obama has a normal presidency.

I will say that his health care reform might define him depending how well it is seen in 10-15 years.