I would recommend that you think really, really hard about whether or not you should apply to your back-up specialty. I applied to a competitive field, and I realized going in that it was pretty much the only field I could see myself enjoying for an entire career (with a very distant 2nd), so my back-up option was to apply again. Make sure you can see yourself being happy in your back-up specialty for the rest of your working life before you decide to apply.
(Now, obviously you can always transfer out, but it's much easier to go into the whole process having thought this through).