Even though Dewey had been beaten in '44 and '48, he apparently was still considered a potential nominee in '52, but he passed on it and instead pushed Eisenhower to run and strongly promoted Eisenhower to become the nominee.
Had he decided to run in 1952, could he have gotten the nomination? And if he did, and picked Ike (which is likely considering he liked Ike), could a Dewey/Eisenhower ticket win in 1952 or would Dewey have been beaten yet again?
Of course Dewey would win, voting against Ike in any form is like voting against your own grandfather!