Had Grant been present in the box, all eyes would have been pointed in his direction and subsequently at Lincoln, making it impossible for Booth to have escaped (Eisenschiml 63). This is because it was the end of the Civil War and at the time Grant was more revered than Lincoln because of his leadership throughout the war.
Additionally, the security measures taken to protect "Honest Abe" were rather vague. Lincoln had specifically made a request to Secretary of War Edwin Stanton that Major Thomas T. Eckert be assigned to him for protection (Bishop 161). One would think that the President of the United States of America would not be denied such a simple favor, but he was. Stanton explained, without actually telling specifics, that he had an important assignment for Eckert that could not be put off (Bishop 162). However, Lincoln was assigned a man from the Metropolitan Police Force. He was John F. Parker, a man who had a major lack of virtue and quite a record. In fact, Parker had many infractions, but hardly any charges stood up in court. One such infraction was when Parker actually fell asleep on a streetcar while on duty. Another charge that he was acquitted of, was being drunk and disruptive in a house of prostitution (Bishop 183). It seems that Parker never learned his lesson; instead he chose to add one more bad action to his reputation. He decided to watch to play himself and left Lincoln completely unguarded (Freedman 123). This in turn, left no one at the state box door and left the President open and accessible. As a result of his actions, an assassin was able to enter the President's state box and freely murder him without a problem.
The final contribution to the success of the assassination was how Booth, before the assassination, left a trail speckled with many clues. These clues were subtle, but nevertheless they did shed little light onto his plans. On many occasions, Booth made his appearance at Lincoln's speeches because he was "impelled to hear the man he hated"(bishop 52).