As New Yorkers go to the polls for the congressional primary on Tuesday, the ballots they cast will have a dubious distinction: Their state is the only in the nation that is holding separate state and federal primary elections in this tumultuous political year.

How and why did that happen?

The practice dates to 2012 when the federal government won a lawsuit compelling New York to move its federal primary elections to the fourth Tuesday in June from September, when they had been held simultaneously with state primaries. The federal government asked for the change because it contended that a September primary did not leave enough time for military and overseas voters to get absentee ballots for the general election.

State lawmakers then could have moved the state primary election from September to June so that they would again line up. Although Democrats favored the switch, Republicans in Albany balked, arguing that because the state legislative session runs through the end of June, they would have no time in their districts to campaign.

New York’s bifurcated primaries, however, have caused the state to spend millions of dollars more; at the same time, having two separate primaries can also suppress voter interest, election law experts and state officials say.