Days before congressional elections in 1874, the unthinkable suddenly seemed likely.

Republican dominance in Washington had been a fact of life since 1861, when Abraham Lincoln became president and the party held sway on Capitol Hill. With the election of Ulysses S. Grant in 1868, the party remained firmly in control — and when Grant was reelected four years later in a landslide, the Republican juggernaut seemed unassailable.

But by the autumn of 1874, the political climate had changed dramatically. An influence-peddling scandal, a depressed economy and lingering Southern white resistance to Reconstruction clouded Republican chances as never before. As Americans prepared to vote in elections that would determine control of the House of Representatives (senators were elected by state legislatures), the end of Republican supremacy in Washington suddenly seemed possible.

“The complexion of the next House of Representatives,” the Chicago Tribune predicted on Oct. 26, “is likely to be Democratic.”

That proved to be a colossal understatement.