This week’s New York magazine cover story on Fox News Channel was fodder on last night’s “Ed Show” on MSNBC and now Fox News is firing back at Ed Schultz‘s guest on the show: former Gov. Ed Rendell, now an MSNBC analyst.

Rendell says the piece reveals details that, “strips away any thin veneer of impartiality that FOX may have, simply because it admits it was a proving ground, sort of a training ground, for presidential candidates.”

Rendell says FNC’s hiring of so many potential candidates as analysts, “really damaged their credibility.”

Fox News EVP Bill Shine tells Politico, “Governor Rendell didn’t seem to have an issue with our ‘credibility’ or ‘impartiality’ when he was trying to shake us down for more money before signing with MSNBC.”

The former Pennsylvania governor, who joined MSNBC in January, has praised Fox News in the past. On “Fox and Friends” during the 2008 campaign, Rendell said, “I think during this entire primary coverage, starting in Iowa and up to the present — FOX has done the fairest job, and remained the most objective of all the cable networks.”