Democratic presidential hopeful Sen. Barack Obama D-Ill., acknowledges the crowd after he speaks at a rally Tuesday, May 20, 2008, in Des Moines, Iowa. Obama declared himself 'within reach' of the Democratic nomination and celebrated in the state where his win in the opening contest of the presidential primary season helped reshape the race. (AP Photo/M. Spencer Green)
US Democratic presidential candidate Senator Barack Obama (D-IL) takes the stage with his daughters, Sasha (L) and Malia (2nd L), and his wife Michelle (rear) at his Oregon and Kentucky primary election night rally in Des Moines, Iowa, May 20, 2008.
(John Gress/Reuters)
Democratic presidential hopeful Sen. Barack Obama D-Ill., his wife Michelle appear together on stage at a rally Tuesday, May 20, 2008, in Des Moines, Iowa. Obama declared himself 'within reach' of the Democratic nomination and celebrated in the state where his win in the opening contest of the presidential primary season helped reshape the race. (AP Photo/M. Spencer Green)
Democratic presidential hopeful Sen. Barack Obama D-Ill., his wife Michelle appear together on stage at a rally Tuesday, May 20, 2008, in Des Moines, Iowa. Obama declared himself 'within reach' of the Democratic nomination and celebrated in the state where his win in the opening contest of the presidential primary season helped reshape the race. (AP Photo/M. Spencer Green)
US Democratic presidential candidate Senator Barack Obama (D-IL) addresses his supporters at his Oregon and Kentucky primary election night rally in Des Moines, Iowa, May 20, 2008. (John Gress/Reuters)
Democratic presidential hopeful, Sen. Barack Obama, D-Ill., leaves after a rally in Des Moines, Iowa, Tuesday, May 20, 2008. (AP Photo/Chris Carlson)
Democratic presidential hopeful, Sen. Barack Obama, D-Ill., and his wife Michelle arrive for a rally in Des Moines, Iowa, Tuesday, May 20, 2008. (AP Photo/Chris Carlson)
Supporters of presidential hopeful Sen. Barack Obama, D-IL, celebrate his projected win in the Oregon Primary at campaign headquarters in Portland, Ore., Tuesday May 20, 2008.
(AP Photo/Greg Wahl-Stephens)
Supporters of presidential hopeful Sen. Barack Obama, D-IL, Aiden Bozman, 4 years-old, held by his mother Amber Bozman as they celebrate at campaign headquarters in Portland, Ore., Tuesday May 20, 2008.
(AP Photo/Greg Wahl-Stephens)