The key to understanding the correct outcome in Lafler v. Cooper rests, in my view, on understanding the difference between an outcome secured by a windfall versus one secured fair-and-square.
I accept that a defendant has the right to effective assistance of counsel at the plea bargaining stage. Bargaining is now the principal means through which charges are resolved, and thus ought fairly to be considered a stage of the prosecution covered by the text of the Sixth Amendment. The question is: Who pays the price if the defendant does not get effective assistance at that stage, and the matter comes up only after the public has paid the bill for a trial whose conduct and outcome are perfectly legal?
Trials are the method designated by the text of the Constitution for the resolution of criminal charges. Once the defendant gets such a resolution, he has received the principal item guaranteed him. It's difficult to understand why a person who gets a legal sentence after a fair trial has a claim enforceable against the government. In any other context, it's unheard of to punish one party for the fact that the opposing party got bad advice from his own lawyer about how to negotiate.