The only problem with that statement? Presidents don't sign constitutional amendments -- they're passed in Congress and then need to be ratified by the states, and the president plays no formal role in the process.
The good old days. That process has been so abrogated and not openly, for so long that the general public has no idea. I'm sure Cain wouldn't realize that himself and wouldn't remember the facts.
A president can't launch wars on their own, they have.
You can't violate multiple amendments in traffic stops, airports, etc...Presidents let it happen.
You can't order gun shops to notify authorities about multiple weapon buys but it's happening.
You can't harass the Amish and indie businesses trying to provide healthy organic food, they have.
These are a few recent examples of absolutely nothing being followed in the proper way if it has anything to do with government.