The latest news on this front comes from a really interesting article at Ballot Access News written by the widely-respected election expert and advocate for third party/independent ballot access Richard Winger. Take a look at this excerpt:

On February 22, the Arizona House passed HCR 2015. It is a proposed constitutional amendment, to require initiatives to receive at least 60% of the popular vote in order to pass. If the legislature approves the bill, then the voters will vote on it, because it amends the state constitution.

The vote in the House was 31-28. The only state that already requires initiatives to receive 60% is Florida.

Continue reading here.