Consider the following passage from today's Washington Post:
Clinton expects victories in West Virginia, Kentucky and Puerto Rico. Obama's team expects to win Oregon, North Carolina, Montana, South Dakota and Guam. That makes Indiana the critical battleground.
No, it doesn't. Looking at Wikipedia, WV, KY and PR combine to offer 134 pledged delegates. Let's assume Hillary wins those primaries by 10% and wins the delegates by a similar proportion. The latter is a reasonable assumption, but the delegate selection rules are a little bit wacky. Obama has been a little bit better about figuring them out, but it probably won't matter here. That would give her a 74-60 advantage (rounding in her favor). Similarly, let's give Obama a 10% advantage in "his" primaries, which are worth a total of 202 delegates. That's fairly generous to Hillary, since he has racked up bigger margins of victory, on average, so far. That puts him ahead with those delegates 111-91 (again rounding in her favor).
So we come to Indiana. Let's again give her the "decisive" 9% victory she got in Pennsylvania. (You may have thought it was 10%, but the media don't understand rounding.) This time we'll round in Obama's favor, which means she ends up winning the Indiana delegates 39-33.
So if Hillary wins the one remaining "battleground", then she'll end up with 204 delegates. Obama, on the other hand, would get...204 delegates. Wow, that just shows how close the race is, doesn't it?
Except it's not. Obama has a lead of about 130 delegates even including Hillary's slight edge in superdelegates. These figures would get him about 100 delegates away from the nomination, with about 300 superdelegates left to endorse. Who thinks more than two-thirds of the superdelegates would be willing to ignore Obama's lead in pledged delegates? Who thinks more than two-thirds of the superdelegates would vote for Hillary even if everything else was tied?
The Washington Post isn't the only offender. Time calls Indiana the "next stop". What about North Carolina, which votes the same day? Well, it's a smaller state, right? Uh, no. Well, it has fewer delegates because of wacky rules, right? Uh, no. It has 43 more. Well, it doesn't count because it's not going to vote for the Democrats in the fall. Hmm, according to the same Time article, "[Indiana]'s a state that hasn't voted for a Democratic presidential candidate since Lyndon Baines Johnson in 1964..." North Carolina at least voted for Carter in '76.
So basically Indiana matters because it has the most dramatic tension. Just remember: none of this coverage is about who is going to be the nominee (it's Obama). All of it is about giving the news media something to talk about for the next two weeks.