Writing In a Candidate Already On the Ballot

[Kleine Scheiße]

This is mostly a random, garbage question, but I've considered doing it and I can't find any information on any states' policies on this. What if, for instance, I cast a write-in vote for "Donald J. Trump" Or "Hillary R. Clinton"? Would this be counted as if it were simply a second ballot line i.e. Liberal and Democratic lines in New York, or would this be counted as a vote for a separate candidate?

[Kleine Scheiße]

Honestly, just to gum up the system a bit. It might create considerable debate with regards to election process law in whatever state you did it in, which would be interesting.