If he (A) actually has something on Trump and (B) is out to "get" Trump ... why wouldn't he just name him?
I suspect there is something deeper going on here, some other actors who have not been named. There were lots of candidates running for various federal offices .... just sayin'...
Could he be talking about campaign staff who thought they were on the short list for a cabinet office? You could refer to that as a “candidate for a federal office.”