Who would stop Obama?

If Obama decided to run a third term who would stop him. If he wrote an EO declaring he could by the time it ran through the courts it would be to late. The republicans wouldn't they have already shown they do not have the stomach. If they did all he would do is claim racism.
The democrats would champion it. In reality who would stop Obama? We know that 4 supreme court justices would say it was legal. Two of them would be on the fence. Alito would most likely cave.