Which party held the House, the Senate, and the presidency during each term — because most of the legislation credited or blamed on a president required Congress to pass it.
A president can propose, veto, and sign, but cannot pass legislation alone. This page lays out which party controlled each chamber of Congress during each term covered by the treatise, since that balance of power shaped which policies could pass, and how they were financed and negotiated.
Unified means the president's party held both the House and Senate for that Congress. Divided means at least one chamber was held by the opposing party. Most four-year presidential terms span two Congresses (elected two years apart), so control can and often does change partway through a term after a midterm election.
| Term | Congress | House | Senate | Control |
|---|---|---|---|---|
| Carter (1977–1981) | 95th–96th (1977–81) | Dem. | Dem. | Unified Democratic |
| Reagan 1 (1981–1985) | 97th (1981–83) | Dem. | Rep. | Divided |
| 98th (1983–85) | Dem. | Rep. | Divided | |
| Reagan 2 (1985–1989) | 99th (1985–87) | Dem. | Rep. | Divided |
| 100th (1987–89) | Dem. | Dem. | Divided (Senate flipped 1987) | |
| Bush (H.W.) (1989–1993) | 101st (1989–91) | Dem. | Dem. | Divided |
| 102nd (1991–93) | Dem. | Dem. | Divided | |
| Clinton 1 (1993–1997) | 103rd (1993–95) | Dem. | Dem. | Unified Democratic |
| 104th (1995–97) | Rep. | Rep. | Divided (1994 wave) | |
| Clinton 2 (1997–2001) | 105th (1997–99) | Rep. | Rep. | Divided |
| 106th (1999–2001) | Rep. | Rep. | Divided | |
| Bush (W.) 1 (2001–2005) | 107th (2001–03) | Rep. | Split 50-50, then Dem. (Jeffords switch, June 2001) | Divided, mid-term shift |
| 108th (2003–05) | Rep. | Rep. | Unified Republican | |
| Bush (W.) 2 (2005–2009) | 109th (2005–07) | Rep. | Rep. | Unified Republican |
| 110th (2007–09) | Dem. | Dem. | Divided (2006 wave) | |
| Obama 1 (2009–2013) | 111th (2009–11) | Dem. | Dem. | Unified Democratic |
| 112th (2011–13) | Rep. | Dem. | Divided (2010 wave) | |
| Obama 2 (2013–2017) | 113th (2013–15) | Rep. | Dem. | Divided |
| 114th (2015–17) | Rep. | Rep. | Divided | |
| Trump 1 (2017–2021) | 115th (2017–19) | Rep. | Rep. | Unified Republican |
| 116th (2019–21) | Dem. | Rep. | Divided (2018 wave) | |
| Biden (2021–2025) | 117th (2021–23) | Dem. | 50-50 (Dem. w/ VP tiebreak) | Unified Democratic |
| 118th (2023–25) | Rep. | Dem. | Divided | |
| Trump 2 (2025–2026, in progress) | 119th (2025–27) | Rep. | Rep. | Unified Republican |
Read against the Policy Impact documents, the pattern is fairly consistent: the most consequential, one-sided legislation in this treatise — ERTA (1981), OBRA-1993, the ACA and ARRA (2009), the TCJA (2017), and the One Big Beautiful Bill Act (2025) — all passed under unified government, generally on party-line or near-party-line votes. Genuinely bipartisan actions in this treatise — the 1983 Social Security Amendments, the 1996 welfare reform law, the First Step Act (2018) — tend to cluster in divided government periods, when major legislation had to draw votes from both parties to pass at all.
This doesn't mean divided government produces better or worse outcomes for inequality; it means the type of policy that can pass differs. Unified government enables large, one-directional swings (in either direction); divided government tends to produce narrower, negotiated compromises, or fiscal standoffs (the 1995–96 and 2023 episodes in this treatise) when no compromise is reached.