The Republican SEC is considering a resolution that would advocate closing the Republican primaries. It makes sense to me, the idea of a party primary is to elect the parties nominee who will support and closest represents that parties views, ideas, ideals and goals.
Lately, in some elections, it has turned into an attempt by some minority parties to weaken the opposing parties candidate or to pick a candidate who doesn't necessarily represent that parties views.
At the top level, on the Republican side of the ticket, this was openly advocated by Rush Limbaugh to help Hillary Clinton make Obama spend money in the primary. It kept Hillary in the race longer then she deserved and had limited success.
On the national Democrat side, this was done to help John McCain gain momentum and pull out some early, open primary state victories, but the same people later allowed him to collapse on the true election day.
At the state level this threw the Democrat party into chaos when Republicans crossed over and helped in the primary election of Rosaland Kurita but it later put the party in a tough spot when they overturned the primary election results because of her (support of Ron Ramsey?) questionable election results.
The primaries are not true state elections. First off, no one is elected. That happens in the general election. The primaries are a party election. They are preformed courtesy of the state to help pick the parties nominee for the election. The party is the final word on the nominee and for that matter, the final word for the people who will help make the selection. They can allow, or disallow, whoever they want to help make the selection. They can even refuse to hold an election and appoint a nominee if they so chose.
If the party only wants people who have the best interest of their party to help decide who that candidate will be, then they should.
The thought is, while some people switch parties, they should be required to do it early, as in before a field is set for the current primary election or have them sit out an election cycle. This would stop last minute switches when a primary is empty on the opposing ticket.
When a person changes party I don't think it is unreasonable to also ask them to sign a paper saying that they pledge or affirm that the party they are switching to, most closely represents their current values and ideals. If they don't want to do that then their reason for suddenly switching should be clear and it is not to help or truly support the party or candidate of their current choosing.