Congress and the Department of Defense procurement bureaucracy are currently arguing over whether it would be prudent to have two suppliers of engines for the F-35. The Pentagon believes that this would cost an additional $4 billion. But those with memories (or the energy to look it up) of the "Great Engine War" in the 1980s, knows that, in the long run, two suppliers are almost always cheaper, and produces two superior products, instead of one mediocre one. Back in the 1980s, the battle was over whether or not there would be one engine supplier for the F-16. Now, it's the same battle all over again for the F-16s successor, the F-35.
The "Great Engine War" made such an impression on all concerned, that GE (one of the major jet engine manufacturers) decided to build a competing engine for the P&W F100, which was then the sole engine available for the F-15. GE knew there were many complaints about the F100, especially among export customers. GE went on to create the F110 engine for the F-15, and made a lot of money doing so. Oddly enough, P&W service, and the overall quality of their F100 engine increased noticeably after the F110 showed up.
This time around, it's the military people who are short sighted, and willing to risk getting lower quality and less attentive support from a single engine supplier for the F-35. The politicians, and many of the pilots who will be flying the F-35, know better.