If elected, Opposition Leader Peter Dutton would cancel $2.2 billion in federal funding for the first stage of Melbourne's Suburban Rail Loop and spend it instead on a long-awaited train line to the city's airport.
Political scientist Zareh Ghazarian said Mr Dutton's move was a big political gamble and could turn the election into a quasi-referendum on the rail loop for Victorian voters.
"The coalition feels it's going to be a vote-turner," the Monash University senior lecturer told AAP.
"It is a calculated decision to stop one project that's been the subject of a lot of controversy and redirect to another project which seemingly enjoys a lot of support across the community."
A 2024 survey of 1000 Melburnians by Ipsos showed 72 per cent supported building a rail line to the airport, compared to 58 per cent for the rail loop.
Mr Dutton's path to victory on May 3 relies on winning outer suburban or mortgage-belt seats, with the route for the $34.5 billion eastern section of the loop passing through marginal electorates the coalition is targeting.
The state Labor government has claimed a mandate to build the rail loop after winning elections in 2018 and 2022.
But independent infrastructure expert Marion Terrill said it was a "sound decision" for the coalition to back away from the loop after Infrastructure Australia called for "exit strategies" to be developed as cost concerns mount.
"It looks like it's going to be a major money sink, even if nothing goes wrong," Ms Terrill said.
However, she warned the airport project also comes with its own risks and more detail is needed on costings, risks and stakeholder engagement.
Infrastructure Partnerships Australia chief executive Adrian Dwyer called for a wider discussion about how federal governments fund transport investment.
"The real debate to be had goes to how the federal government moves to replace the retreating tide of state investment," he said.
That uncertainty will have a knock-on effect to investor confidence across Victoria, according to the McKell Institute's state executive director Rebecca Thistleton, who was previously an adviser to the state Labor government.
"We need both major parties to be talking about actual plans for infrastructure, not just cherry picking projects based on a particular day of whose votes it is they're trying to get," she said.
