Did a search and no recent threads..... We bought the TT late last fall. Didn't really spend much time putting her away properly. I'm guessing the powercord is most likely where they got in, but ...
If you have an Agway type place or possibly online, look for coyote urine. I know, sounds gross but just a few drops around your TT, on the tires etc. keeps them out. Suggested to a friend last fall. He tried it and now swears by it. Not a single mouse as opposed to the 2-3 he finds every other year.
Just a thought. I've used Bounce in cabinets etc. nice fresh smell and it seems to work inside as well.