They lack guts on gas tax
Both major party candidates for president believe, in the abstract, in spending money for the building and repair of public structures. They support such spending, both because the infrastructure is deteriorating and because the building and repair of infrastructure would serve as an economic stimulus.
They also support, in the abstract, government having the money to pay for what it buys.
Going beyond the abstract in both cases could only mean increasing the federal fuel tax which has been 18.4 cents per gallon since 1993. The diesel fuel tax is 24.4 cents per gallon.
Neither major party presidential candidate has the courage to support what is clearly needed.