The sentence is as follows: "Isn't it evident who/whom they have in mind for the position?"
Depending on how you try to reword it to figure it out, the answer seems different.
--Is it not evident that he is the one they have in mind for the position? (This seems to be a case for "who" here.)
--Is it not evident that they have him in mind for the new position? (This seems to be a case for "whom" here.)
Should it be who or whom? Why?