New voter registration data for the 29 states (plus D.C.) that have registration by party shows that Libertarian registration has risen 8% since October 2008. UPDATE: the original post said Libertarian registration was up 11%. At the time I wrote it, I had current official data for all but two states, Massachusetts and Florida. For those two states I had used unofficial data. Now I have received the official data, and it turns out my unofficial data for Florida had included inactive voters, and the unofficial data for Massachusetts had been wrong for another reason.
All other nationally-organized parties lost registrants. The number of registered voters in the 29 states (plus D.C.) that have registration by party declined since October 2008, because states purge their lists in between elections.
The June 1, 2010 printed Ballot Access News will have a table showing the number of registered voters in each state, in each party. More voters are registered Libertarians now than ever before. Between October 2008 and this spring, Libertarian registration rose in 19 of the 23 states that tally Libertarians. It declined in four states, Colorado, Nevada, Oregon, and South Dakota. The decline in South Dakota isn’t surprising because the party has not been on the ballot there since 2006.