Your weekly mileage. The quality and length of your long runs. A quality taper. Fresh legs. The weather. Hydration. Nutrition. Course support. A positive outlook.
But do you know the real key to the perfect marathon? Of course. The outfit. And mine has been selected and tested.
Quite appropriate for Indianapolis in the fall, don't you think?
p.s. - I killed yesterday's 22 miler wearing that combo. The run couldn't have gone better.