Here is video of Sen. Arlen Specter interrupting his Democrat rival Joe Sestak as Sestak was delivering his closing remarks before a Progressive Forum.
The two were to have separate Q & A sessions before the group. Specter looked like he did not realize Sestak was even speaking when he climbed onstage during Sestak's remarks. Sestak paused, and greeted the Senator. The moderator got up and asked Specter to leave the stage until Sestak was done! Sestak seemed embarrassed for Specter, and tried to lighten the mood with some humor.