Barack Obama officially became the Democratic presidential nominee when Ohio cast its 188 votes and put him over the required 2,778 delegates.

Just after midnight Wednesday, party secretary Alice Germond briefly paused the state-by-state roll call to announce "Barack Obama is now our party's official nominee!" while some delegates danced to Kool and the Gang's, "Celebration." 

The roll call came after delegates were fired up by former president Bill Clinton's 50-minute nominating speech. Obama briefly joined Clinton on stage at the end of his speech, and the two embraced and waved to the roaring crowd.

Obama will make his acceptance speech Thursday night.