The Obama campaign announced Monday that he will leave the hall of the Democratic National Convention in Denver and deliver a rock-star-style acceptance speech at Invesco Field at Mile High, quadrupling his live audience. The speech will be on the fourth and final day of the convention, Aug. 28. Adding to the historic resonance of the first African-American to be nominated for president, that’s also the 45th anniversary of Martin Luther King Jr.’s “I Have a Dream Speech.” The move means additional expense for the television networks, where executives are having a conference call Monday to discuss the expense and...