Those costs, financial and political, could be significant. Canberra Liberals, not the natural choice of Canberra voters, have effectively set the agenda for next year's election by declaring their intention to rescind any contract for the tramway. This decision received considerable publicity recently, surprisingly well after the decision had been taken. Certainly, I knew of it about six months ago.

Even now the party is unwilling to disclose publicly too much of how it would go about dismantling a multi-million dollar contract, but there is reasonable confidence it could avoid significant penalties should this occur. The most obvious escape would be to convert any tramway infrastructure begun before next year's October election to a dedicated busway between Gungahlin and Civic.

After all, it was Capital Metro Minister Simon Corbell who undertook in 2005 to outline a proposal in about six months for a multi-million dollar Northbourne Avenue busway. Corbell was then, reasonably enough, persuaded of the value of busways having been shown successful projects in Queensland.

But his proposal for a Northbourne Avenue busway did not materialise.

The significantly extra cost then and now of a discrete rail service in Canberra could not be justified and further, as recognised by most transport specialists, will reduce public transport benefits to about 80 per cent of Gungahlin residents.

There is considerable disquiet over the government's legislation aimed at preventing any formal public objection to the project. In opposition, Corbell campaigned strongly against redevelopment and against the use of call-in powers by planning ministers. Now he presides over a project largely based on potential redevelopment and in which he has sought to muzzle opposition.

He might not like to be reminded of it, but on September 21, 2011, Corbell told the ACT Legislative Assembly, "The Greens once again adopt a completely unrealistic, unstrategic and unconsidered approach to the real challenges of transport in this city, all because they want to jump on the wagon, forgive the pun, of rail." The subsequent political manoeuvring is worth reflection. As Chief Minister, Katy Gallagher, no doubt conscious of the need for Greens support, committed in September 2012 to a light rail line between Gungahlin and Civic if re-elected in the 2012 election. Yet the Greens lost three of their four assembly seats and Liberals gained two, leaving Labor and Liberals each with eight of the 17 seats. The Capital Metro project was included in a formal agreement between ACT Labor and the ACT Greens, who sole surviving MLA, Shane Rattenbury, effectively held the balance of power.

But to claim the 2012 election gave a mandate for the construction of a project, which in all likelihood will cost more than $1 billion just to build, to any person or party is at best tenuous. Aside from the cost, there was no disclosure then that about 80 per cent of Gungahlin residents and effectively all Kaleen and Giralang residents will lose direct bus services to Civic and beyond to boost patronage on Capital Metro. Neither has the option of a dedicated busway been evaluated by the government.

Yet all transport specialists with whom I have discussed the matter believe a busway could be built in much less time and for about 10 per cent of the cost of the Capital Metro project. Given the traffic priorities being flagged for the tram, buses would complete the journey up to 10 minutes faster and would have the flexibility to travel elsewhere from the Civic and Gungahlin tram terminuses.

From these details alone, it is easy to understand why Canberra Liberals believe this is perhaps their best chance of winning government. But there is more. In a city where public transport attracts only about eight per cent of commuters; where the proposed tram would and already is eroding existing bus services; and where the estimated minimum capital cost per household is about $5400; the project does not have broad support.

Even within Gungahlin, only about six per cent of its 50,000 residents would live within 400m of a tram stop and about 20 per cent within 800m. Of the latter, most now have direct bus services to Civic and beyond.

Very few residents of Tuggeranong, Woden, Weston Creek, Molonglo, South Canberra or Belconnen will derive any benefit from this project. And of those who could, the prospect of higher rates based on the government's claimed increased land values will raise serious doubts as to the merits of the project which will see Northbourne Avenue's tree-lined vista turned into an industrial scar.

With 25 seats up for grabs at next year's election, a party will have to gain at least three seats in three electorates and two in the other two to have a majority. Meanwhile, the government says it will sign a contract for the light rail well before the election, leaving voters to balance a possible financial penalty if it is cancelled against the indicative far greater cost of the project should it go ahead.

Meanwhile, Labor and Liberal have the opportunity to clarify their positions. Labor to clearly state the full capital cost of the project and its likely operating cost. Estimates on the latter vary from $20 million to $40,000 annually.

Liberals not only have to clarify how they would manage any cancelled contract for light rail but what they would put in its place. People would then have a base to compare the relative merits of both policies.

Graham Downie is a Canberra writer.