Many times students who have applied to a campus, whether Princeton or another, and gotten wait listed or even rejected, can build after a year or more of college elsewhere the credentials to successfully transfer in.
Better still, there will be a new Transfer Common App in 2018 making the transfer process that much easier, especially for the nontraditional applicants, to submit transfer applications to multiple campuses. According to the Common App: "This new transfer application will not only better serve returning adult students (over the age of 25, now representing 38% of undergraduates) and students applying from community colleges (43% of all undergraduates), it will also facilitate the process for recommenders and member institutions."