This is the latest of a regular segment on The National tracking the Liberal government's performance on its campaign promises. Watch Chris Hall's full report on The National, tonight at 10 p.m. on CBC Television or 9 p.m. ET on CBC News Network.

Thumb through the Liberals' 2015 election platform and it doesn't take long to come to the heading "Investing to Strengthen the Middle Class."

Topping the long list of commitments is the most expensive one of all: another $60 billion over 10 years for infrastructure — that's on top of what the previous Conservative government planned to spend, a commitment that effectively doubles what the federal government will spend on infrastructure over the next decade.

"We will invest in now in the projects our country needs and the people who can build them," the platform reads. "Interest rates are at historical lows, our current infrastructure is aging rapidly and our economy is stuck in neutral.

"Now is the time to invest."

But the Liberal plan is not just to sink money into building arenas and community centres or repairing roads and bridges.

The plan is to spend a third of that $60 billion on public transit, another third on what's called social infrastructure such as affordable housing, seniors centres and day care facilities. The final third will be directed to green projects, such as improving water treatment plants, clean energy projects and measures to protect against climate change.

It's ambitious. It's expensive. And it's critical to Prime Minister Justin Trudeau's intention to transform Canada's economy into one built on sustainable development and less dependant on fossil fuels.

The problem for the government is where to begin. The prime minister suggested  Tuesday's budget will start small.

"The first two years we're going to do the unsexy things that governments hate to announce," he told a business audience this week in New York. "Recapitalization of infrastructure. Maintenance upgrades. The things you don't get to cut ribbons and announce shiny new buildings on."

'Super sexy' spending

Reading that, it's hard to argue with Trudeau. The price tag may add up to $10 billion over the next two years. But filling potholes, fixing roofs on public buildings or upgrading signal systems on a subway line don't exactly make voters stand up and cheer, let alone attract media attention.

On the other hand, big city mayors, well, they love the idea.

"I happen to think that's super sexy because nothing is sexier than an arena bathroom that doesn't have mould, or a roof that doesn't leak," Calgary Mayor Naheed Nenshi said in an interview on CBC Radio's The House.

Nenshi and Trudeau

Calgary Mayor Naheed Nenshi says his city is ready to move on infrastructure projects - all that's needed is promised federal funding from Prime Minister Justin Trudeau's government. (Jonathan Hayward/Canadian Press)

"We're absolutely happy to spend money on new builds, on affordable housing. These are all areas I'm looking forward to seeing some action from the federal government on in the budget."

For Nenshi and others, it all adds up to jobs. Thousands of jobs, at a time when the economy is slowing and jobs are being shed.

And there are suggestions that Finance Minister Bill Morneau will add an extra incentive when he brings down his first budget on Tuesday by increasing the federal government's normal contribution of one-third of the total cost of these kinds of projects to as much as half, a recognition that cities don't all have the money to start such work this fall.

But others argue that the mantra of "jobs now" can't come at the expense of investing in projects that will facilitate long-term growth. For example, many economists say building more social housing, while greatly needed, doesn't lead directly to greater growth.

"People are expecting action,'' Sean Speer, a senior fellow at the Macdonald-Laurier Institute in Ottawa, acknowledged earlier this year at a meeting of the Federation of Canadian Municipalities.

"But the worst thing the government can do now is focus on the short-term at the expense of the long-term."

The long-term depends far more on building new rapid-transit systems and roads. And on investing in new technology and innovation, including projects that will help reduce greenhouse gas emissions.

Those things will create jobs, too, just not as many and not as quickly.

So the prime minister is trying to find that delicate political balance with his government's first budget. On one hand, acting now to create jobs, on the other signaling that the government is laying the groundwork for those long-term projects that won't be of obvious benefit to voters until well after the next election.

Sunday Scrum: Federal budget 201611:15