ABC's George Stephanopoulos reports: Sen. John McCain, R-Ariz., wants to win the election in November. But he does not want to steal Sen. Barack Obama's, D-Ill., thunder this evening, as the Democrat becomes the first African American to accept a major party's nomination for president. A senior McCain campaign official tonight said the news of the Republican's running mate, which is scheduled to be announced tomorow in Dayton, Ohio, will not upstage Obama tonight."There will be no announcement tonight. There will be no leak tonight. This is Barack Obama's night. His nomination is a singular achievement. Tonight's his night to make his case," a senior campaign official said.Earlier today, the McCain campaign issued an unusual ad, congratulating Obama on his historic achievement of accepting his party's nomination 45 years to the day after Martin Luther King Jr. delivered his "I Have a Dream Speech.""This is truly a good day for America. ... Tomorrow, we'll be back at it, but tonight, Senator, a job well done," McCain says in the ad.