Nixon once said a vice-presidential candidate can't help you, but he can certainly hurt you.
I would say personality can help marginally but can certainly hurt, a lot.
In a competition between two similarly attractive men personality can be a pretty decisive factor. It goes way beyond basic social skills. It includes things like how you dress, how you carry yourself, mannerisms, ability to influence, ability to command a room, psychological penetration, projection of power, personal chemistry, and a myriad of subtleties.
I would go so far as to say a 6 with their shit together, given the right arena, could beat an 8.
The world's a complicated place. I find the biggest struggle this forum has is with uncertainty and complexity.