In order to vacate a plea based on ineffective assistance of counsel, a defendant must show that his attorney's performance was deficient and that he was prejudiced by this deficiency. This latter requirement is objective, not subjective, and thus, a petitioner must convince the court that a decision to reject the plea bargain would have been rational under the circumstances. It is difficult for a petitioner to make this showing if the evidence of his guilt was overwhelming, even if he states that he would have preferred to go to trial (no matter how small the odds of success) to try to avoid the immigration consequences that would certainly accompany the offered plea.
The court affirmed its prior holding that "no rational defendant charged with a deportable offense and facing 'overwhelming evidence' of guilt would proceed to trial rather than take a plea deal with a shorter prison sentence." The possibility of jury nullification cannot be considered when determining if a rational defendant would have rejected the plea.
The full text of Lee v. United States can be found here: