The issue at hand is small, even for local politics: the sudden closure, over four days, of a pair of access lanes from Fort Lee, in New Jersey, on to the George Washington Bridge into New York.
But in this traffic mystery, Democrats see a potential scandal that could permanently harm Republican New Jersey governor Chris Christie, who has been riding high as a prospective 2016 presidential candidate.
In September, two of Mr Christie's top appointees at the Port Authority of New York and New Jersey ordered the lanes abruptly shut to traffic, causing days of gridlock in Fort Lee. Democrats allege that the move was political retribution against the town's Democrat mayor, Mark Sokolich, for not endorsing Mr Christie for re-election this year.
With Democratic legislators and the news media continuing to dig up emails and other evidence, the two appointees involved in the lane closure have resigned.
Mr Christie has claimed no advance knowledge of the incident and has denied any wrongdoing on the part of his administration. But that has not kept Democrats in Washington from pouncing.