As first reported on PoliticsPA -- by the soon-to-be-National-Journal-bound Alex Roarty -- President Barack Obama will campaign for Joe Sestak on Sept. 20 in Philadelphia. Obama, of course, backed Sen. Arlen Specter in the Democratic primary and used Bill Clinton to try to get Sestak out of the race. And Sestak also recently said he'd rather have Michelle Obama campaign for him than her husband. Memories are short in politics, people, and you can bet Sestak is grateful for a presidential appearance, which he hopes will help turn out the Democratic base that's suffering from a serious enthusiasm gap right now.

Here's my piece from the main site:

By Daniel Malloy
Post-Gazette Washington Bureau
WASHINGTON – President Barack Obama will campaign for Rep. Joe Sestak during a presidential swing through Pennsylvania on Sept. 20.
The Sestak campaign confirmed this morning that Mr. Obama will appear with the Democratic Senate nominee in Philadelphia. The event was first reported by PoliticsPA.
“We're honored that the president would do an event with Joe during his trip to Pennsylvania,” Sestak spokesman Jonathon Dworkin wrote in an email. “He and Joe may have had their differences, but they can agree that it is critical to elect a senator who will put Pennsylvania's working families first.”
Mr. Obama campaigned for Mr. Sestak’s opponent, Sen. Arlen Specter, in the Democratic primary race after he successfully enticed the five-term Republican to switch parties. Mr. Obama’s administration also reached out to Mr. Sestak through former President Bill Clinton to keep him from running in the primary. Mr. Clinton, according to a version of events provided by the White House and Mr. Sestak, offered the second-term Congressman from Delaware County an unpaid advisory role on national security matters but Mr. Sestak nipped the discussions in the bud.
Though Mr. Sestak has been a fierce advocate for Mr. Obama’s agenda – from the stimulus bill to health care and Wall Street reform – the primary fight and the president’s sinking popularity have kept Mr. Sestak from aligning too closely with the president on the campaign trail thus far.
Mr. Sestak in July told reporters in Harrisburg that if he had his pick of White House surrogates, he’d choose First Lady Michelle Obama.