# 1866 Midterm Elections [[Andrew Johnson]] administration midterm. One of the most consequential midterms in American history: the **Radical Republicans** won veto-proof supermajorities in both chambers, structurally enabling **Congressional Reconstruction** that overrode Johnson's lenient-Reconstruction policies and produced the 14th and 15th Amendments. The election is conventionally treated as a referendum on Johnson's Reconstruction policy — and a decisive repudiation. ## Result - **House:** Republicans won veto-proof supermajority (~173 of 226 Republicans vs. ~47 Democrats in the 40th Congress) - **Senate:** Republicans won veto-proof supermajority (~57 of 71 Republicans) - **Chambers flipped:** None — Republican supermajority consolidation - **Net change:** Republican gain of ~37 House seats and ~10 Senate seats; one of the largest single-cycle Republican gains ## Notable - The 1866 result enabled **Congressional Reconstruction** (1867 Reconstruction Acts dividing the South into military districts, requiring [[Fourteenth Amendment]] ratification for readmission) - The **14th Amendment** (passed by Congress June 1866) and **[[15th Amendment]]** (passed February 1869) were ratified during this Congress and the next - **Andrew Johnson's impeachment** (1868) was made operationally possible by the Republican supermajority this election produced - The Confederate states began reentering the Union under Congressional Reconstruction terms from 1868 onward; this is one of the canonical **realigning midterms** ## Connections - [[Andrew Johnson]] — Sitting president; impeached by the Congress this election produced. - [[Ulysses S. Grant]] — Future president; the Republican landslide signal predicted his 1868 nomination and victory.