Large corporations tend to support Republicans because their CEO's see in as being in the immediate interests of their share-holders to do so. However, Boeing today lost a huge contract to EADS, for the tankers (flying gas stations) that will support our Air Force for the next 40 years or more. Don't be misled by even the $40B price tag, when you consider extended support this contract will probably be worth two or three times that amount over the next half century. However, sometimes there are factors that corporations believe are even more urgent, and that may result in the unexpected: Boeing could wind up being a strong supporter of an Obama candidacy in the general election
Boeing corporate executives may believe that John McCain had something to do with their loss of this contract. He did take a strong public position against Boeing in earlier efforts to get the tanker contract without a bid. I don't believe that is true, but after a big competitive loss in the aerospace industry (and this is monumental) there can be huge emotional swings, and sometimes grown adults begin to act irrationally. It may be more convenient to blame the loss on an imagined vendetta of a Senator than to acknowledge internally that their proposal and product was just not good enough.
So how might Boeing respond? Well, the worst case would be a McCain Presidency, where the EADS deal would safely go through. They might hope for an Obama win, then use the excuse of defense cuts to argue that development of a new tanker should be stopped. This stops EADS from getting into the market, and then might allow Boeing to argue 5-10 years downstream that the current tanker procurement was based on obsolete technology and the competition should be started over.
I can't guarantee that this will happen, but it certainly is plausible scenario. If we see signs, it will go to show that there is more going on under the surface of the military-industrial complex than one might guess.