Possible Clues:

• Two presidents ago
• Senator who wrote 'Dreams From My Father'
• Winner of 2008
• Kagan's appointer
• President born furthest from Washington, D.C.
• 2008 "Yes We Can" sloganeer
• ''Dreams From My Father'' author
• Appointer of Kagan and Sotomayor
• President between Bush and Trump
• President with a Nobel Prize