Fold? With 5 Open Championships under his belt already? With other Major wins there at Turnberry?
Tom Watson may not win, but if he doesn't I will guarantee it's not because he 'folded'. He may get beat by someone else having a spectacular round but it won't be because he beat himself, like Marino on Day 3.
It's his course, his style, his time.... Oh, and he's not nervous. 0.0% chance of 'folding' IMHO.
The only question is can he hold the pack at bay while he shoots his best.