Who watched yesterday's presidential debate held in Mississippi? According to Nielson TV ratings, lots of people in battleground states like Colorado, Ohio, North Carolina and Virginia.

Another interesting finding: Half of the 10 biggest markets for the debate were in the South.

Here are Nielson's ratings for cities where the most people watched the event:

1. St. Louis -- 52.1%, 649,000 households
2. Memphis -- 49.5%, 330,000 households
3. Baltimore -- 47.1%, 515,000 households
4. Washington, DC -- 44.6%, 1,030,000 households
5. Nashville -- 44%, 424,000 households
6. Greensboro-H.Point-W.Salem -- 42.2%, 285,000 households
7. Columbus, OH -- 41.5%, 377,000 households
8. Norfolk-Portsmth-Newpt News -- 41.4%, 298,000 households
9. Richmond-Petersburg -- 40.3%, 211,000 households
10. Denver -- 39.7%, 586,000 households

The numbers in Greensboro, North Carolina were likely boosted in anticipation of Sen. Obama and Sen. Biden's visit to the area for a rally today, which drew a crowd of 20,000 people and cemented NC's status as a key swing state.