Mrs. Pelosi may be tempted to pad her House Democratic margin by reviving a practice used extensively between 1875 and 1903. The Constitution provides that each congressional chamber “shall be the judge of the elections, returns and qualifications of its own members.” Using this clause, both parties routinely expanded their majorities during the Gilded Age by challenging the minority’s narrow or suspect victories and replacing them with their own or declaring the seat vacant, provoking a time-consuming special election. Between the 44th Congress (1875-77) and the 58th (1903-05), the parties flipped a total of 59 seats through such challenges.

There have been similar disputes since the founding—the first expulsion was in 1792—but they took on a highly partisan cast after 1874, when Democrats won the House for the first time since 1856. The new majority unseated three Southern Republicans and flipped close contests in Illinois and Massachusetts. In the next Congress, Democrats replaced five more Republicans, including a Californian who’d won by a single vote, a Floridian whose margin was three votes and a Bay Stater who’d prevailed by five. In the following Congress, the 46th (1879-81), the Democrats’ margin was so narrow they played it straight, ousting a Democrat and a Republican.