[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2010/images/05/18/art.rendellspecter0518.gi.jpg caption="Gov. Rendell, right, huddled with Sen. Specter, left, and Specter's wife on Tuesday in Philadelphia."]
(CNN) - Some political observers have wondered why the White House opted not to send President Obama or Vice President Biden to Pennsylvania to campaign with Sen. Arlen Specter in the final weeks before Tuesday's Democratic Senate primary.
Related: Specter scrambles to keep seat
Pennsylvania Gov. Ed Rendell, a Democrat, offered one theory during an appearance on CNN's "Campbell Brown."
Asked about Obama's and Biden's notable absence from the Pennsylvania campaign trail in recent weeks, Rendell said it might be "because their last minute appearances in New Jersey and Virginia and Massachusetts didn't serve too much good."
As evidence of his short coattails, many of the president's critics have pointed to his failure to help Democratic candidates in those three states. Last November, Republicans won governorships in New Jersey and Virginia and earlier this year, Republican Scott Brown won a special election in Massachusetts to replace the late Democratic Sen. Ted Kennedy.
But after offering his theory, Rendell was quick to defend the president's schedule when it came to Pennsylvania.
"Let me tell you, there isn't a Democrat in this state who went to the polls who didn't know that Barack Obama wanted Arlen Specter elected," Rendell said.