Mr Coe believes that, provided no work begins on the $780-million infrastructure project before October 2016, a new incoming government will be able to cancel it at minimal cost to taxpayers. Even if a firm deal was inked before 2016, Mr Coe believes ACT taxpayers would still be be liable for no more than $30 million in compensation, were contracts cancelled by a new Liberal government. According to Mr Coe, that $30 million figure is based, pro rata, on the Victorian Labor government's offer of $339 million compensation to a construction consortium to walk away from a planned $6.8 billion toll road in Melbourne.

The ACT Liberals' opposition to light rail and its threats to dismantle are a matter of public record. Mr Coe's preparedness to put a price on how far the Liberals will go to undo what the Labor government maintains is now a fact of life (the choice as to who builds, owns and operates the line has been whittled down to two consortia) is audacious, however. Parties of the centre-right rarely invoke the tactics of their left-wing political opponents as justification for their own plans. That business leaders and senior Coalition politicians have all condemned the Victorian government's "recklessness" in tearing up the toll road contract illustrate the extent to which the ACT Liberals have gone out on a limb. Whether this is a sound tactic, justified by the tantalising prospect of an election win in 2016, or a crazy-brave manoeuvre depends very much on individual perceptions as to what light rail can and will bring to Canberra.

There is a view that light rail is a sensible investment decision for a rapidly growing city whose heavy reliance on private motor vehicles cannot continue. This group accepts that a nascent light rail system will require substantial public subsidies for some decades hence, but believes that it will, in time, prove a worthwhile addition to the city's public transport network. Then there is the alternative view, generally put far more vehemently, that the investment in light rail is justifiable neither on transport nor economic grounds, and that building it would be an indulgence for a city mired in budgetary problems. It would also be a crippling drain on public finances for years to come.

Economists at the Productivity Commission charged with examining competing transport infrastructure options on the basis of utility, return on capital and cost-benefit analysis have cast doubt on light rail too, declaring that buses are as good an alternative and far cheaper. Even among supposedly agnostic economists, however, consensus has been hard to establish. Labor's business case presented last November suggested that for every $1 spent on the Capital Metro link, $1.20 would accrue in community benefits. This is a far from compelling cost-benefit ratio, however, and critics have since cast further doubt on that number, with one even suggesting the analysis was characterised by "a disturbing lack of facts on the table". However, the Barr government can rightly claim that it went to the 2012 election with a clear policy enunciating its intention to get light rail beyond the design stage and to begin work "several years" hence.

For better or worse, Labor can justly claim to have a clear mandate to have work on the Capital Metro project well underway before the next election. And for the Coalition to claim otherwise smacks of arrogance. The Victorian government gave as its No 1 reason for reneging on the East West Link Liberal Premier Denis Napthine's decision to sign contracts just weeks before the state election and in defiance of care-taker conventions. No such issue is likely to arise here, although it would be foolish to assume this (or any) government would not stoop to locking its successors into carrying out its signature projects. Mr Coe is warranted in pointing out the government's lack of wisdom in embarking on an expensive project at such an inopportune moment. But in choosing to make it a wedge issue, he is flirting with lighted matches.