Lee Drutman and Beau Tremitiere have this article in Bulwark, advocating that states legalize fusion. They favor disagregated fusion, which is the type that lets the voter chose which party he or she supports, when voting for a candidate who is the nominee of two parties. Thanks to Political Wire for the link.
The authors are advisors and supporters to the Moderate Party of New Jersey, which has a lawsuit in New Jersey state court, arguing that the New Jersey Constitution requires the state to permit fusion.