Democratic presidential hopeful, Sen. Barack Obama, D-Ill., receives a honorary degree during the commencement ceremony at Wesleyan University in Middleton, Conn., Sunday, May 25, 2008. Filling in for Sen. Edward M. Kennedy, D-Mass., and tying himself to the family's legacy, Obama urged college graduates to 'make us believe again' by dedicating themselves to public service. (AP Photo/Chris Carlson)
Democratic presidential hopeful, Sen. Barack Obama, D-Ill., speaks during commencement at Wesleyan University in Middleton, Conn., Sunday, May 25, 2008. Filling in for Sen. Edward M. Kennedy, D-Mass., and tying himself to the family's legacy, Obama urged college graduates to 'make us believe again' by dedicating themselves to public service. (AP Photo/Chris Carlson)
Democratic presidential hopeful, Sen. Barack Obama, D-Ill., speaks during commencement at Wesleyan University in Middletown, Conn., Sunday, May 25, 2008. (AP Photo/Chris Carlson)
Democratic presidential hopeful, Sen. Barack Obama, D-Ill., reacts to a student during commencement ceremony at Wesleyan University in Middleton, Conn., Sunday, May 25, 2008. Filling in for Sen. Edward M. Kennedy, D-Mass., and tying himself to the family's legacy, Obama urged college graduates to 'make us believe again' by dedicating themselves to public service. (AP Photo/Chris Carlson)
Democratic presidential hopeful, Sen. Barack Obama, D-Ill., reacts to a student during the Commencement ceremony at Wesleyan University in Middletown, Conn., Sunday, May 25, 2008. (AP Photo/Chris Carlson)
Democratic presidential candidate Senator Barack Obama greets supporters during a rally campaign event at the Old San Juan in San Juan, Puerto Rico, May 24, 2008. (Ana Martinez/Reuters)
Democratic presidential candidate Senator Barack Obama (D-IL) speaks during a rally campaign event at the Old San Juan in San Juan, Puerto Rico, May 24, 2008. (Ana Martinez/Reuters)
Democratic presidential hopeful Sen. Barack Obama, D-Ill., talks with a secret service agent as he takes a walk with supporters during a campaign stop in Old San Juan, Puerto Rico, Saturday, May 24, 2008. Obama visited Puerto Rico ahead of the June 1 primary. (AP Photo/Brennan Linsley)
Democratic presidential candidate Senator Barack Obama speaks a few words in Spanish to supporters during a rally campaign event at the Old San Juan in San Juan, Puerto Rico, May 24, 2008.
(Ana Martinez/Reuters)
A security agent arrives to take up a position before the arrival of Democratic presidential hopeful Sen. Barack Obama, D-Ill., for a campaign stop in Old San Juan, Puerto Rico, Saturday, May 24, 2008. Obama visited Puerto Rico ahead of the June 1 primary. (AP Photo/Brennan Linsley)
A crowd cheers as they watch the arrival of Democratic presidential hopeful Sen. Barack Obama, D-Ill., during a campaign stop in Old San Juan, Puerto Rico, Saturday, May 24, 2008. Obama visited Puerto Rico ahead of the June 1 primary. (AP Photo/Brennan Linsley)