The state-level opposition is a reminder of the challenge of building a national transportation project in the United States: while the federal government can set priorities, the construction is up to the states.

With recent polls showing all of the anti-rail Republican candidates leading or within striking distance of their pro-rail Democratic rivals, it is possible they could be elected and try to stop the train projects.

Federal officials, meanwhile, are incredulous that candidates are threatening to spurn stimulus money that their states competed ferociously to win just a year ago.

“The bottom line is that high-speed rail is a national program that will connect the country, spur economic development and bring manufacturing jobs to the U.S.,” Transportation Secretary Ray LaHood, a former Republican congressman, said in a statement. “It will also transform transportation in America, much like the Interstate highway system did under President Eisenhower. It’s hard to imagine what would have happened to states like Ohio and Wisconsin if their leaders had decided they didn’t want to be connected to the rest of the country back then.”

Several candidates said they wanted to spend the stimulus rail money on roads and bridges, but it is unlikely they would be able to do so without changing the law: the stimulus, which included $28 billion for roads and bridges, required that the $8 billion for rail projects be spent on rail projects.

Federal officials declined to speculate on what would happen if anti-rail candidates were to win. But states that turn down rail money would probably have to return it to the federal government, which could then award it to states that want it.