Some commentators have therefore sought to develop non-partisan popular electoral models. Dr Michael Duffy, along with co-authors Dr Steve Perryman and Anthony Cianflone, have floated the concept of 'tri-partisan endorsement' of a candidate by the three largest parties, who would then face a national popular vote. This idea, which is an evolution of a proposal by the late Professor George Winterton made after the failed 1999 referendum, seeks to deliver a politically neutral head of state who will be a symbol of unity. It involves constitutional provisions that would bind the major political parties to such endorsement. Another proposal is the ‘Jones-Pickering Model’ developed by Dr Benjamin Jones and Professor Paul Pickering. Under this model, eight different candidates are nominated by two-thirds of a joint sitting of each of the six state and two territory parliaments and then each go on to a popular national vote.