I really don't think Custer could have become President no matter what he did. Remember that he had to beg and plead to be allowed to go back to the 7th Cav before the LBH fight -- he was close to being court martialed again. Also, his permanent rank was Lieutenant Colonel -- he was brevetted to Brigadier General during the Civil War and reverted when the war was over to his permanent rank; to call him "General" was to apply a courtesy title.

He was a daring and brave person, but I think he lacked a lot of good sense. Most of his troopers disliked him, and Reno and Benteen REALLY didn't care for him or he for them. (Benteen, by the way, was sent off to scout around the LBH battle area carrying all the spare ammunition with him. Custer himself sent a note recalling him; Benteen may or may not have hurried in response.)

Custer was also a martinet (but many military leaders were at the time) and was big on nepotism -- Tom Custer rode with his brother at the LBH.

Recent archeology work at the Greasy Grass battlefield, especially involving the recovery and siting of spent bullets, give a fascinating picture of what happened.