GOP should win IN somewhere around 53-45% (third party candidates may get 1-2%).
McCain lost it in '08 simply because the economy really collapsed at the wrong time, late in that campaign and many abandoned his shape.
Also, he had to gamble at other states he needed to win and could not waste time in IN. He had to assume he would win there, which of course didn't happen
A Republican nominee really needs to win the state almost 60-40 show evidence of an impending win nationwide. A 53-48 split of the Indiana vote means that the Democrat is winning Ohio about 51-48. A Republican nominee who loses Ohio is not going to be elected President.
I can't imagine Hillary Clinton making many appearances in Indiana unless it is to help Indiana Democrats.