excise taxes on gasoline and the municipal grants pegged to them are levied on volume, not price. The less gasoline people buy for private automobiles, therefore, the lower the value of federal grants for public transit. If those grants were pegged to sales rather than excise taxes, they would be the next thing to a perfect carbon tax.
Meanwhile, the free market is applying its own time-tested solution to the problem of overconsumption, with salutary political as well as social consequences. Hillary Clinton never stooped lower than when she promised a summer "gas-tax holiday," joining John McCain in the promise. Barack Obama never looked better than when he condemned it.

