Nielsen is reporting that in the top 56 local markets,  the combined overall household rating for last night’s final presidential debate between Barack Obama and John McCain was 38.3.  That’s down 8.8% from last Tuesday’s 42 household rating.   Baltimore had the most household viewing as a percentage with 49.3% of the households watching the debate, followed by the Washington, D.C market with 48.4%.  You can download the household ratings detail for all of the top 56 markets [PDF].