No spoilers please. I only watch the show and have not devoted years of my life to reading the books... yet. If you haven't watched last night's episode, there are spoilers below.

Joffrey is dead. Who is next in line to the throne? Obviously, I know there is a war going on with several outsiders claiming the throne. But if the proper protocol* is followed, who takes Joffrey's spot? Joffrey is half Lannister and half Baratheon**, so would a Lannister or a Baratheon be heir to the throne. Sorry if this is a stupid question or has already been answered, but I haven't caught it.

* This of course assumes that there is some type of general lineage that is normally followed.

** Yes, I know he is actually pure Lannister. However, most people don't seem to know that for sure or at least acknowledge it.

ETA: POTENTIAL SPOILERS in Thunder Lips response below but not really if you go back and watch season one it has already been explained.