WASHINGTON - JUNE 4: Democratic presidential hopeful Sen. Barack Obama (D-IL) looks through the window of his vehicle on Capitol Hill June 4, 2008 in Washington, DC. Senator Obama, who claimed his party's nomination after his delegate count surpassed 2,118, visited Capitol Hill to vote on a budget resolution before traveling to New York City.
WASHINGTON - JUNE 4: Democratic presidential hopeful Sen. Barack Obama (D-IL) speaks with reports on Capitol Hill June 4, 2008 in Washington, DC. Senator Obama, who claimed his party's nomination after his delegate count surpassed 2,118, visited Capitol Hill to vote on a budget resolution before traveling to New York City.
WASHINGTON - JUNE 4: Democratic presidential hopeful Sen. Barack Obama (D-IL) speaks with reports on Capitol Hill June 4, 2008 in Washington, DC. Senator Obama, who claimed his party's nomination after his delegate count surpassed 2,118, visited Capitol Hill to vote on a budget resolution before traveling to New York City.
WASHINGTON - JUNE 4: Democratic presidential hopeful Sen. Barack Obama (D-IL) hugs Senator Debbie Stabenow (D-MI) on Capitol Hill June 4, 2008 in Washington, DC. Senator Obama, who claimed his party's nomination after his delegate count surpassed 2,118, visited Capitol Hill to vote on a budget resolution before traveling to New York City.
WASHINGTON - JUNE 04: Democratic U.S. presidential candidate Sen. Barack Obama (D-IL) waves after speaking at the 2008 American Israel Public Affairs Committee (AIPAC) Policy Conference at the Washington Convention Center June 4, 2008 in Washington, DC. Obama has claimed his party's nomination after his delegate count surpassed 2,118.
WASHINGTON - JUNE 04: Democratic U.S. presidential candidate Sen. Barack Obama (D-IL) waves before speaking at the 2008 American Israel Public Affairs Committee (AIPAC) Policy Conference at the Washington Convention Center June 4, 2008 in Washington, DC. Obama has claimed his party's nomination after his delegate count surpassed 2,118.
WASHINGTON - JUNE 04: Democratic U.S. presidential candidate Sen. Barack Obama (D-IL) is seen speaking on a video projection during the 2008 American Israel Public Affairs Committee (AIPAC) Policy Conference at the Washington Convention Center June 4, 2008 in Washington, DC. Obama has claimed his party's nomination after his delegate count surpassed 2,118.
WASHINGTON - JUNE 04: Democratic U.S. presidential candidate Sen. Barack Obama (D-IL) speaks during the 2008 American Israel Public Affairs Committee (AIPAC) Policy Conference at the Washington Convention Center June 4, 2008 in Washington, DC. Obama has claimed his party's nomination after his delegate count surpassed 2,118.
U.S. presumptive Democratic presidential nominee Senator Barack Obama (D-IL) arrives on stage to speak at the American Israel Public Affairs Committee (AIPAC) policy conference in Washington June 4, 2008. Obama said on Wednesday Iran posed a serious threat in the Middle East and vowed to stop it from acquiring a nuclear weapon at the pro-Israel lobby group's conference.
WASHINGTON - JUNE 04: Democratic U.S. presidential candidate Sen. Barack Obama (D-IL) acknowledges the crowd after he addressed the 2008 American Israel Public Affairs Committee (AIPAC) Policy Conference at the Washington Convention Center June 4, 2008 in Washington, DC. Obama has claimed his party's nomination after his delegate count surpassed 2,118.
WASHINGTON - JUNE 04: Democratic U.S. presidential candidate Sen. Barack Obama (D-IL) shakes hands with senior AIPAC officials after he addressed the 2008 American Israel Public Affairs Committee (AIPAC) Policy Conference at the Washington Convention Center June 4, 2008 in Washington, DC. Obama has claimed his party's nomination after his delegate count surpassed 2,118.
WASHINGTON - JUNE 04: Democratic U.S. presidential candidate Sen. Barack Obama (D-IL) waves after he addressed the 2008 American Israel Public Affairs Committee (AIPAC) Policy Conference at the Washington Convention Center June 4, 2008 in Washington, DC. Obama has claimed his party's nomination after his delegate count surpassed 2,118.
WASHINGTON - JUNE 04: Democratic U.S. presidential candidate Sen. Barack Obama (D-IL) waves after he addressed the 2008 American Israel Public Affairs Committee (AIPAC) Policy Conference at the Washington Convention Center June 4, 2008 in Washington, DC. Obama has claimed his party's nomination after his delegate count surpassed 2,118.
WASHINGTON - JUNE 04: Democratic U.S. presidential candidate Sen. Barack Obama (D-IL) addresses the 2008 American Israel Public Affairs Committee (AIPAC) Policy Conference at the Washington Convention Center June 4, 2008 in Washington, DC. Obama has claimed his party's nomination after his delegate count surpassed 2,118.