This is not "declaring your major," and you don't really have to list anything, as many high school seniors are undecided on what their majors will be and, as the school well knows, many will change their minds before actually "declaring" their major.
It should have no effect on your chances of admission. Tufts is aware, for example, that many people apply because of its top flight International Relations and pre-med curricula. That being said, if you have a real and demonstrable interest in a major that is less popular, then you should say so.
My recommendation is to be sincere and truthful. The AdCom can detect a phony from100 yards.