Third in seniority, O'Connor has, deliberately or not, become the "swing" justice, with her moderately conservative views often the deciding factor in close 5-4 votes.
Though an avowed liberal, his closest match turned out to be Bill O'Reilly, the flame-throwing conservative host of The O'Reilly Factor on the Fox News Channel.
The other factor for Obama would be with fiscally conservative Blue Dog Democrats and other Democrats who stood with Obama on the middle-class tax pledge.