Caught this kernel of information buried in a local article about the Obama campaign whistle-stop in Reading, PA two days ago. I was surprised that I hadn't heard some of this information previously.
For this stop, Obama had a couple well-known supporters behind him, both politically and physically. Reading Mayor Tom McMahon, along with the mayors of Lancaster and York, officially announced their endorsement today.
Link
Now, I had heard that the Lancaster Mayor had endorsed Obama previously, but the endorsement of the Reading and York mayors appears to be new. This South Central area of Pennsylvania is an important area for Obama, as it's population is akin to the white, rural areas where he has performed well, and it also has a mix of students, highly-educated voters and African-Americans (in Harrisburg) that can help with the organization for the campaign.
As kos has said several times, in most places the only endorsements that really matter are governors and especially mayors, because they have networks, organization and local connections that can provide a solid base of support.
If we want to keep Clinton's margins low in Pennsylvania, Obama would be well served to perform well in this area of the state.