In their study of Senate advertising two weeks ago, Nielsen reported Joe Sestak was doing most of his advertising in the Pittsburgh market. In their latest report (going over ad time the week of Sept. 20) they show the Democrat has moved the balance of his ads to the vote-rich but more expensive Philadelphia market.

Pat Toomey continues to get balanced on-air mentions in the Pittsburgh market, while a huge majority of Sestak's were in Philly (partially explained by Obama's campaign visit to the city that week).

Here's the full Nielsen report:

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