Voting by faculty after a Search Committee recommends a candidate for a TT hire
I'm sure it varies from one place to another. In my experience, our search committee (TT position at an R1) had to come to an agreed upon decision in terms of the order in which we were going to recommend candidates (#1, #2, #3). From there, our recommendation had to be approved by the dean of our college, and from there the offer was made.

If you're asking about what criteria a committee uses for recommending candidates, a lot of aspects are weighed: how the campus visit went - particularly the research presentation, publication record/plans, does this candidate's research align with and complement what the department already offers or is there too much overlap with other faculty, can we see this person fitting in our department, can they teach what we need them to teach, etc. Ultimately, however, the big question is always: who is most likely to stick around and manage to get tenure according to our standards? In other words, who's the safest investment?