Only Colin Barnett in Western Australia, while reaffirming that he is a republican, declined to sign the statement sponsored by the Australian Republican Movement, which read simply that the signatories "believe that Australia should have an Australian as our head of state".

Notably the seven signatories included three Coalition leaders, Mike Baird, of NSW, Will Hodgman, of Tasmania, and Adam Giles, of the Northern Territory. Baird in particular, likely to be a long-serving NSW premier, is an important voice and a significant ally of Prime Minister Malcolm Turnbull.

Support from political leaders is a necessary but not sufficient condition for reform, as 1999 showed in states where both the state government and the opposition supported change but the popular vote was lost. But such a united republican stand, supported by the Prime Minister, the opposition and the Greens at the Commonwealth level, is unprecedented. That was not the case in 1999.

Barnett's stated reasons for declining to sign may signal future debates if they resonate with Turnbull. Barnett told ARM chairman Peter FitzSimons that he "did not think that the time is right ... to prosecute the argument for constitutional change", though he believed Australia would become a republic in his lifetime. As Barnett is 65 and the ARM is proposing a plebiscite to begin the process in five years, one can only wonder at Barnett's timetable for action.

He may agree with Turnbull that change should wait until the passing of Queen Elizabeth as Australian head of state. The ARM disagrees as does South Australian Premier Jay Weatherill who not only regards not waiting for the transfer as "the ultimate act of respect to Queen Elizabeth", but also predicts that she could preside over such a transfer in "the elegant and expert way in which she's handled her relationship as head of state so far".

What must be differentiated are two very different things: a strategic decision by republican advocates, based on careful reasoning, and any suggestion that it is somehow inappropriate for Australia to decide its own timing. That must be up to the Australian people. The Prime Minister holds the strategic view as he sees no benefit in a second heroic failure.

Turnbull faces a big test this year as we enter a potentially groundbreaking reform era for causes that he has long supported, such as same-sex marriage and Indigenous constitutional recognition. How they are handled will shape his leadership.

He will need to be both shrewd and bold to successfully ride these reform waves. In supporting reform he will face considerable opposition within his own party, including from former prime minister Tony Abbott. Success will breed success and his authority across the country and within his own party will rest on his ability to win elections.

That is where Labor and Bill Shorten enter the conversation. Election victories are always the highest priority for political parties whatever their beliefs. Shorten must balance his support for reforms with his natural desire to press Turnbull harder for some action instead of mere talk. Strong Labor promises on speedier reforms will attract some voters to Labor's side. Ultimately Turnbull may have to be satisfied with a moderate position somewhere between his own Coalition conservatives, including not just Abbott but also members of his own cabinet, including the Nationals, and the Labor opposition.

The ARM must also continue to be energetic and shrewd. It must meet Turnbull's challenge to become a larger and more popular movement. That means that republican petitions in support of republican political leaders must be repeated again and again, ultimately enlisting not just 10,000 plus signatories but many times that.

It should welcome but not rely on media support which can breed confusion. Media reports of the premiers and chief ministers' declaration showed this. They looked for dissension over timing and confusingly referred to the "United States of Australia" when they know that the American model is not under consideration.

ARM should likewise encourage and welcome but not rely on support from high-profile community leaders. General David Morrison's listing of the republican cause among his three core aspirations as the 2016 Australian of the Year came at just the right time for republican momentum. Furthermore, as a former chief of the army he may be able to explain republicanism within Australian military circles in a language which it understands. The majority of the military, with notable exceptions such as former ARM head Mike Keating, has so far been unenthusiastic about an Australian as head of state.

But that will not be enough either. Many, perhaps most, recent Australians of the Year have supported the republican cause and some, like mental health leader Professor Patrick McGorry and businessman Simon McKeon, have been active advocates.

The necessary momentum will come from a combination of parliamentary and community leadership and demonstrated popular support. The latter is the most important and building such support, measured ultimately in petitions and public opinion polls, is the challenge that recent republican prime ministers, including Turnbull, have issued to the republican movement. The ARM has had a most rewarding last 12 months but must repeat that year after year. Like Australian tennis players striving to win a grand slam it must demonstrate resilience, perseverance and continued growth.

John Warhurst is an emeritus professor of political science at the Australian National University and former chairman of the Australian Republican Movement

John.Warhurst@anu.edu.au