jetBlue is Chuck Schumer's baby. He is practically a founder of that company. He got them their JFK slots. It was all about "low fare competition" in the NYC market. He won't allow that to end.
Plus, a liberal Democrat antitrust division under Eric Holder will never allow further concentration of market power at Kennedy. Not to mention that LaHood would also have some say in the matter on anti-trust grounds as well as transfer of the slots. He shot down the slot swap at LGA by imposing huge divestiture of slot requirements and would undoubtedly do the same thing if we try to buy jetBlue and their JFK operation. Probably give them to Southwest.