This is how you try to minimize a post-convention bounce. From Justin Miller at PolitickerOH:

John McCain will hold a 10,000-strong rally in Ohio the day after Barack Obama accepts his party's nomination in Denver.

On Friday, Aug. 29 McCain will hold a rally in Dayton, according to the Hamilton Co. Republican Party chairman's blog and confirmed by a GOP source. The source said McCain will hold the event at Nutter Center and that the party expects 10,000 or more attendees.

Assuming the campaign gets that much it still won't compare to the tens of thousands (and the millions on TV) that watch Obama accept the nomination at Invesco Field the night before. But it's the opportune time for McCain to steal the spotlight and make his VP announcement.