Hmm.  After confirming reports that the McCain camp was preparing to make their first local ad buy in Indiana, Politico's Ben Smith reports that the campaign is now denying any such plan:

A McCain spokesman, Michael Goldfarb, says the campaign is not planning to advertise in Indiana. An RNC spokesman says there are no RNC/McCain hybrids going up in the state.

Regardless, Smith adds that the Republican National Committee's independent expenditure outfit is reportedly exploring an ad buy in the Hoosier State:

At least one of my sources mistook a national network buy running in Indiana for a local buy. The other, however, points to the RNC's independent expenditure arm, whose presence in Indiana would indicate roughly the same things, and which is said to be requesting rates there.

I see two possible scenarios here.  On the one hand, the McCain campaign may really believe their own hype (i.e., that Indiana isn't a "true battleground state" this year).  On the other hand, the expanded electoral playing field may have them stretched so thin that they simply can't afford to devote resources to Indiana, instead relying on the RNC to help them out.