Cain would autograph life amendment

Herman Cain tried to clean up the running confusion over his position on abortion last night, but in the meantime opened questions about his grasp of the Constitution.

In an interview with David Brody last night, Cain said he'd sign a pro-life constitutional amendment if it crossed his desk as president.

“Yes. Yes I feel that strongly about it. If we can get the necessary support and it comes to my desk I’ll sign it," he said. "That’s all I can do. I will sign it.”

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.

Candidates have in the past pledged to support such an amendment, but it's not clear what signing one would mean.