In defense of exclusive primaries
Primaries are a good thing, and should remain under the control of the political parties. While Indiana technically has a "closed" primary, the enforcement is nonexistent, allowing people to cross back and forth or (worse) monkeywrench the other party's primary. Now comes a Herald-Times editorial arguing for an open primary system - one that would defeat the entire purpose of primary elections.
As a Republican, I have no business deciding who the Democratic nominee for Mayor will be. I am not going to be voting for the Democratic candidate, and that decision is best made by Democratic voters. Note that I said Democratic "voters" instead of Democratic party activists. After all, party activists are a small subset of the primary voters who choose the nominees. This is why the Herald-Times' argument for allowing voters to participate "whether they are active in a party or not" is a classic Straw Man logical fallacy.
I am not sure why the H-T is complaining that the primary system somehow violates people's privacy. There are many good reasons why someone's election participation is public record. One reason is it protects against voter fraud: It is important to have the voter list be verifiable. Everyone can look up who voted in a primary or general election. Even if someone votes in a primary, it does not mean that person will vote for all - or even any - of that party's general election nominees. When someone votes - though not for whom they voted - should always be public record.
The primary election already results in the top vote-getter for each party making it to the November general election, though there are two separate pools of voters instead of only one. That means the nomination is already decided by the voters. This is why, nationwide, there have been many candidates who have been chosen by voters when the political parties would have chosen someone else. One big example is Barack Obama, who most likely would not have been the Democratic nominee for President in 2008 if that was decided only at a convention instead of primary votes.
Some have argued for nominating conventions instead of taxpayer-funded primary elections. The problem with this is it does not give the voters a choice of who will represent them on the ballot. The other problem is that party insiders may choose a poor candidate, while winning a primary election at least demonstrates that candidate has the support of the party's voters. There have been a number of elections where the nominees would have been very different if chosen by the party establishment instead of the voters. And while not having taxpayers fund a primary sounds good on paper, it is never going to happen. You will never see that choice taken away from voters.
The primary system is a good one. All it asks is that the voters who pick the party's nominees pick one party or the other. Having an open primary where all voters can choose both parties' nominees is an invitation for mischief and severely dilutes what it means to be a Republican or a Democrat. Strong political parties, and clear differences between the parties, is good for democracy. It should remain that way, and separate primaries ensure that. If anything, Indiana's closed primary system should be more restrictive, not less.