Retiring North Dakota Democratic Sen. Byron Dorgan plans to campaign for Pennsylvania Democratic Senate candidate Joe Sestak Thursday afternoon in Philadelphia at a job training center.

Dorgan will be the third nationally recognizable headliner for Sestak who strikes a moderate and post-partisan tone.

In recent weeks, New York City Mayor Michael Bloomberg, an independent, and former Nebraska Sen. Chuck Hagel, a Republican supportive of President Obama, traveled to the Keystone State on behalf of the congressman and former Navy admiral.

When Dorgan announced his retirement earlier this year, sources said he was tired of the partisan bickering in the Senate, and he and a long-serving colleague were overheard "bitching and moaning about how it just wasn't the same." Sestak has begun to position himself as less partisan than his Republican opponent, former Rep. Pat Toomey, and is getting attention for that message.