The text of the amendment doesn't say so explicitly, but Ineffective Assistance of Counsel is grounds for overturning convictions: https://en.wikipedia.org/wiki/Ineffective_assistance_of_coun...

(Note that the standard requires both that your counsel was ineffective, and that his/her ineffectiveness caused your conviction)

On the one hand, it'd be absurd if it did. On the other, it would often come in handy.