I bet DDL was laughing himself to sleep every night knowing that he was able to convince a bunch of Yanks to call a Brit "Mr. President" for 6 months!!! He is awesome. DDL for President!!!
Is there any possibility he literally loses his identity to this character and lives the rest of his life as if he is actually Abe Lincoln?
Only reason I'd say no is that he's done this so many times for so many other great roles, and he hasn't had any problems yet. The guy is not human.