It's fine to support the President until such time as he proves himself unsupportable. To even state that means that you already have some idea of what would qualify as crossing the line. Unless you are just trying to be contrary then you should be able to state what that line is. By doing so you can both clearly explain your position to everyone else, while at the same time proving that you aren't moving the goal post. Otherwise, you make yourself out to be a blind supporter, in which case it makes no difference to me which side of the aisle you sit on, you are worse than useless.
Disclaimer: I have largely avoided this discussion because I am 1) not a Republican, 2) not a Democrat, and 3) not butthurt one way or another over this past election. In my opinion, there really wasn't a winning option.