The phrase "unlikely candidate" means that someone or something is not expected or does not seem to be a suitable or probable choice or option for a particular situation or position. Full definition
Growing up, I was a pretty unlikely candidate for the life I'm leading today, at least, that's what it looked like from the outside. (gerardadams.com)
The two newcomers seemed unlikely candidates to change that situation, because both had spent most of their time in college blocking for real running backs. (si.com)
In addition to why, many of those things, make me the most unlikely candidate to blog pictures of what I wore. (stillbeingmolly.com)