Nope, these are not marginal seats. How does a toll road swing seats towards LNP. LNP would of built the same thing, instead passing though Brooklyn and Sunshine, instead widening the existing freeway alignment.
LNP doesn't even have any public transport alternative for the west of Melbourne. So why would they switch government.
ALP is already gonna widen roads throughout the western suburbs, throughout its next term. LNP has zilch.
ALP going to remove a crossing in Williamstown, two crossings in Werribee and one more in Aircraft. LNP wanna grade seperate roads instead.
Sure thing there hasn't been a rail centric project in the west, if you exclude the Ballarat upgrades, Regional Rail Link, a station in Caroline Springs, & removing the Altona shuttle service. Of course they could do much better, such as improving the Werribee line and Regional Rail Link (make it a metro service eventually). As well as improving other modes, especially buses.
But this West Gate Tunnel, as bad as a project it is, would not necessary be the total reason for the seats swinging.
Crime is a major issue in the west and due to the LNP scare tactics may persuade some voters. That sudden decision with the Youth Justice centre in Werribee may change voters stance on the west.
But Infrastructure unlikely would be a main reason, due to the LNP not showing any interest in rail projects, which is what the West Gate Tunnel protests want. ALP are the only ones that are delivering both public transit and roads. LNP only interested in roads.