If you find yourself in a stopped train in a Hudson River tunnel, or in a vehicle on a choked highway, in coming years, at least you will know why. In his drive to become the darling of the cut-costs-at-all-costs Republican crowd, Gov. Chris Christie of New Jersey ignored real economic analysis and relied on exaggerated worst-case scenarios to kill the largest public transit project in the nation in 2010.

The project, two new rail passages under the Hudson River, would have vastly improved the region’s economy, the environment and the lives of millions of commuters. The federal government and the Port Authority of New York and New Jersey were providing most of the $10 billion needed to build the tunnels. But Mr. Christie said they were going to cost a lot more than that and that New Jersey would be on “a never-ending hook.”

Now, a report from the Government Accountability Office makes it clear that the cost-cutting talk was political bluster. Mr. Christie estimated that the project could cost more than $14 billion, of which New Jersey would have had to pay 70 percent if you counted federal stimulus dollars and Port Authority money. The report said later federal estimates ranged from $9.8 billion to $12.4 billion and that the state’s real share was 14.4 percent. The benefits would have been huge. Today, traffic moves under the Hudson River through two 100-year-old tunnels that are nearly at capacity at peak travel times. With projections that transit demands in this area will increase 38 percent by 2030, the new tunnels would have allowed twice as many trains during rush hour, 48 per hour instead of 23.

The report, which Mr. Christie continues to dispute, cited estimates that home values and tax revenues would have risen, and that the construction would have added $9 billion to the regional economy. But Mr. Christie wanted to use the tunnel money to avoid adding a few cents to the state’s gasoline tax, the nation’s second lowest. He was thinking about his career, not his constituents.