The carbon tax was the fiscal centrepiece of Patrick Brown's platform.

One Conservative author of the platform went so far as to say on Twitter “if you drop the carbon tax, there is no 'rest of the platform.' No middle class tax cut, no childcare refund, no mental health investment, no dental care for low income seniors.”

But the secret is that it didn't just raise a bit of money. It raised a LOT of money, and its abandonment leaves the PC Party in a giant fiscal hole.

The reason is buried in the back of Patrick Brown's platform document is a little footnote explaining the $2.4 billion figure for the carbon tax:

“(2) This represents the difference between projected revenue from Ontario's cap-and-trade program and projected revenue from Federal carbon pricing. For prudence we have assumed exit from cap-and-trade as of July 1, 2019 so 2019/20 revenues include a final three months of cap-and-trade revenue. If we can exit January 1, 2019, the new federal carbon price revenue would increase slightly. Given the potential volatility associated with cap-and-trade pricing, this approach will provide more certainty for families and businesses.”

Economist Mike Moffatt confirmed that this means the total revenue loss is not just the $2.4 billion attributed for the carbon tax revenue at maturity in the platform costing. It is also the $1.9 billion a year that the current Liberal cap and trade program raises. That money funds a variety of economic development, environmental and energy programs across the province.

The logical inference is that the PC Party platform planned to abandon the GreenOn programs and others funded by cap and trade, then raise a total of $4.3 billion at maturity from the carbon tax.

Certainly, the CTF pledge the leadership candidates signed commits them to end both the carbon tax and eliminate the existing cap and trade program while rejecting the federal scheme. The answer from the three leadership candidates on how to plug the fiscal hole has been “cut Liberal waste.”

But Brown's platform already included a large value for money audit to find $2.8 billion in savings within government.

All told, the new PC Party leader will have to find:

• $2.4 billion a year for the carbon tax, plus
• $1.9 billion that was the Liberal cap and trade revenue made up by the proposed PC carbon tax according to the footnote, plus
• $2.8 billion from the Patrick Brown audit commitment.

That's means by the final year of a PC government they are going to need to find $7.1 billion in annual savings.

So how big is $7.1 billion in annual spending in the Ontario government? Is this money you find under the sofa cushions?

For starters, the visible examples the PC Party hold up as waste don't come close to meeting the target.

For instance, this past summer the government spent $120,000 for a touring giant rubber duck to help celebrate Ontario 150. While the PCs pointed to that as waste, it would have taken more than 59,000 cancelled ducks to meet their waste target.

Other examples like e-Health or gas plants are decisions years ago that can't be changed to avoid future costs or raise revenues.

To put this in perspective, according to his own announcement, Tim Hudak's 100,000 jobs pledge saved $2 billion a year. Now the PC Party needs to find $7.1 billion.

The 2017 Ontario budget and other published reports document some potential levers in the $141 billion in expenses in the Ontario budget:

$54 billion of that $141 billion is health care, mostly hospitals, pay for doctors and nurses, and drugs. According to table 6.13 in the Ontario budget, a 2% reduction in total health spending – hospital budgets, doctor pay, nurses pay, eligible drugs - nets about $1 billion.

$26.5 billion is schools, and 80% of that is a straight-line function of collective agreements with teachers and the cap on class sizes. Increasing class sizes in primary school by two kids is estimated at about $250 million.

$8.4 billion is post-secondary education, again mostly wages. The Liberal policy for free tuition grants for low income students is estimated to cost about $145 million a year.

$17 billion is the social safety net: disability and welfare transfers, services for children in care, housing for the developmentally disabled, and the like. Reducing the welfare support caseload by 10% would save $250 million.

$5 billion runs the justice system and OPP. Ending the replacement of municipal police with OPP for court security saves $125 million.

All those reductions save under $2 billion.

Even cutting hospitals and medical staff wages, increasing school class size, ending free tuition, a 10% reduction in welfare cases and no OPP in courts is not even one third of the way to closing the PC funding gap.

Abandoning the carbon action pledge is far more than giving up on a tool for fighting greenhouse gases. For the PC Party, it sets their entire fiscal framework on fire.

Andrew Steele is a management consultant in Toronto. He served as an advisor to Premier Dalton McGuinty and  had senior roles in election campaigns at the federal, provincial and municipal level.