Was it Democratic Presidential Nominee Barack Obama or NBA star and Olympic Gold Medalist LeBron James who was the big audience draw for the “Late Show with David Letterman” on Wednesday night? We may never know, but the ratings were terrific. CBS reports that the Nielsen overnights from 55 metered markets posted a Household rating of 4.1 and a 10 share. That tied the second highest rating for Late Night in the 2007-2008 television season. Also, CBS was happy to point out, it was the fourth time this season that Letterman has beaten NBC’s “Tonight Show” with Jay Leno when both aired original shows.