At their Monday debate in Nashua, Democratic candidates for governor Jackie Cilley, Maggie Hassan and Bill Kennedy concurred that one key to New Hampshire’s economic success would be shaped like a commuter train.

Such a fantasy is not confined to Democrats. Many Granite Staters are under the delusion that commuter rail is an unmitigated economic and transportation benefit.

There is a reason New Hampshire does not have commuter rail: It is that commuter rail in a state this sparsely populated is an enormous waste of resources. The state Department of Transportation studied the feasibility of adding a commuter rail line to I-93 when planning its expansion. The DOT opted to subsidize bus service instead. The department’s own study concluded that commuter rail was not cost-effective and would not reduce traffic congestion.

Commuter rail is a subsidy — on the order of hundreds of millions of dollars — to a tiny fraction of the mostly middle-class commuters who live in New Hampshire and work in Massachusetts.

There is no good case for building publicly subsidized commuter rail in New Hampshire at any time, and the case for it is made even weaker by our current economic situation. When the state struggles to fund its courts, prisons, highways and social services, the idea that we should devote scarce resources to a cushy ride to Boston for mid-level executives is preposterous.

At least Cilley and Kennedy suggest that they would raise taxes to bring this 19th-century commuting option to New Hampshire. Hassan pretends that we can avoid a broad-based tax and have commuter rail, too. The right option for New Hampshire is to avoid both.