By Madeleine Heffernan
It is Opposition Leader Tony Abbott's "pledge in blood" - to repeal Labor's price on carbon.
And with polls putting Labor's primary support at below 30 per cent, it's a prospect that needs strong consideration.
But as the Minister for Mental Health and Ageing Mark Butler points out, promises to repeal complicated laws are difficult to pull off.
"Well, we tried rollback on the GST; it didn't work. This is the mother of all rollback campaigns,'' Butler told Q&A on ABC Television last night.
Deutsche Bank has looked into the Coalition's promise to repeal the carbon tax, and says it might not happen until April 2014 - nearly two years after the legislation first takes effect in July this year.
"Each step in the constitutitional process takes time, and in practice, it could take 8-14 months for the repeal bills to pass, with risks of further delay at each stage of that process," reseach analyst Tim Jordan writes.
"On that timetable, the earliest a repeal bill could pass after an August 2013 election would be April 2014, 22 months after the carbon price comes into force."
Assuming the Coalition wins the next election but is not granted control of the upper house, Labor and the Greens are unlikely to repeal the price on carbon, leaving Abbott with the option of calling a 'double dissolution' - or fresh election on all seats of parliament.
Jordan says only three of Australia's six double dissolution elections so far have returned the sitting government, and only one has given the incumbent control of both houses.
If the Coalition fails to win control of both houses of parliament through the double-dissolution election, it could then call a 'joint sitting' to pass the contested legislation, provided it has a majority of seats in the two houses.
But whether this is the ideal outcome is another issue: Mr Jordan says abandoning a market mechanism for reducing emissions would ''only provide a temporary reprieve for major emitters".
"The carbon price is likely to have a modest impact on most listed emitters: most high-carbon firms in trade-exposed sectors will receive free units (and in the case of steelmakers, cash grants) to offset the impact; resources companies face a small impact relative to earnings; airlines will pass on the cost in ticket prices; and utilisies are likely to recover most of their additional costs through higher electricity prices," he writes.