Political eras of the United States refer to a model of American politics used in history and political science to periodize the political party system existing in the United States.

The United States Constitution is silent on the subject of political parties. The Founding Fathers did not originally intend for American politics to be partisan. In Federalist Papers No. 9 and No. 10, Alexander Hamilton and James Madison, respectively, wrote specifically about the dangers of domestic political factions. In addition, the first President of the United States, George Washington, was not a member of any political party at the time of his election or throughout his tenure as president.Chambers, William Nisbet (1963). Political Parties in a New Nation. Furthermore, he hoped that political parties would not be formed, fearing conflict and stagnation, as outlined in his Farewell Address.

Generally, the political history of America can be divided into eras in which partisan hegemonic control of the federal government (either through unified partisan control of the Presidency and Congress, or when a Congress of the opposing party to the President is out of session) occurs for a continuous majority of time. These hegemonic eras are:

1789–1801: Federalist Era, dominated by the nationalist-leaning Federalists, and their ideological predecessors in the Pro-Administration Faction, both based in the Northern United States. 1801–1861: Democratic Era, dominated by the liberal-leaning Democrats, and their ideological predecessors the Democratic-Republicans, both based in the more slave sparse Southern U.S areas to the non-coastal Northern counties. 1861–1933: Republican Era, dominated by socially liberal and economic conservative Republicans based in New England and the Great Lakes Region (and later the greater Rust Belt region and the Midwestern United States). 1933–1969: New Deal Democratic Era, dominated by a coalition of socially conservative Democrats based in the South and economically progressive Democrats based in the greater Rust Belt region, the Sun Belt and the West Coast of the United States. This marks the beginning of the "party switch" – liberals in the North and Urban Cities slowly flip Democratic. 1969–Present: Divided Government Era, where the Federal Government is predominantly divided (between Presidency and/or Congress when an oppositional Congress is in session). Power is split between liberal Democrats based in the North and West Coast & conservative Republicans based in the Midwest and South. This marks the finalization of the "party switch" – conservatives in the South and Rurals slowly flip Republican. A process that was completed by the 2010s and the start of the Trump era. The political significance of these five defined eras can be reinforced by the feature of each era beginning with near-unanimous Electoral College presidential victories that occur alongside the election of a unified trifecta of House, Senate and President for the hegemonic party (or alongside the election of divided government in the fifth era):

Washington's first unanimous election in 1788–89 was won with a unified trifecta of Pro-Administration members (ideological predecessors to Federalists). Thomas Jefferson and James Monroe's re-election landslides in 1804 and 1820 respectively were won with unified trifectas of Democratic-Republicans (ideological predecessors to Democrats). Abraham Lincoln's landslide re-election in 1864 as the candidate of the Republican-affiliated National Union Party was won with a unified Republican trifecta. Franklin D. Roosevelt's landslide election to a second term in 1936 was won with a unified Democratic trifecta. Richard Nixon's landslide re-election and Ronald Reagan's two landslide elections, in 1972, 1980, and 1984 respectively, were won alongside the election of divided governments (Nixon lost both Houses of Congress while Reagan lost the House of Representatives both times).

Using these hegemonic eras as a framework, the more detailed specifics of party realignments and the seven party systems they take place in are described in detail below:

First Party System: Federalist & Democratic-Republican Hegemony

The "First Party System" began in the 1790s with the 1792 re-election of George Washington and the 1796 election of John Adams, and ended in the 1820s with the presidential elections of 1824 and of 1828, resulting in Andrew Jackson's presidency.

George Washington's cabinet

The beginnings of the American two-party system emerged from George Washington's immediate circle of advisers, which split into two camps:

Federalists – John Adams and Alexander Hamilton emerged as leaders of this camp; electoral base is in the North. They were the right leaning party of the era. Democratic-Republicans – Thomas Jefferson and James Madison emerged as leaders of this camp; the electoral base is in the South and Non-Coastal North. They were the left leaning party of the era.

Ironically, Hamilton and Madison wrote the Federalist Papers against political factions, but ended up being the core leaders in this emerging party system. Although distasteful to the participants, by the time John Adams and Thomas Jefferson ran for president in 1796, partisanship in the United States came to being.Richard Hofstadter, The Idea of a Party System: The Rise of Legitimate Opposition in the United States, 1780–1840 (1970)Gordon S. Wood, Empire of Liberty: A History of the Early Republic, 1789–1815 (Oxford History of the United States)

Era of Good Feelings

This era was dominated by the Democratic-Republican party as the Federalists became irrelevant. The disastrous Panic of 1819 and the Supreme Court's McCulloch v. Maryland reanimated the disputes over the supremacy of state sovereignty and federal power, between strict construction of the US Constitution and loose construction. The Missouri Crisis in 1820 made the explosive political conflict between slave and free soil open and explicit. Only through the adroit handling of the legislation by Speaker of the House Henry Clay was a settlement reached and disunion avoided.

Jacksonian democracy

"Jacksonian democracy" is a term to describe the 19th-century political philosophy that originated with the seventh U.S. president, The United States presidential election of 1824 brought partisan politics to a fever pitch, with General Andrew Jackson's popular vote victory (and his plurality in the United States Electoral College being overturned in the United States House of Representatives).

With the decline in political consensus, it became imperative to revive Jeffersonian principles on the basis of Southern exceptionalism. The agrarian alliance, North and South, would be revived to form Jacksonian Nationalism and the rise of the Democratic-Republican Party. As a result, the Democratic-Republican Party split into a Jacksonian faction that was regionally and ideologically identical to the original party, which became the modern Democratic Party in the 1830s, and a Henry Clay faction that regionally and ideologically resembled the old Federalist Party, which was absorbed by Clay's Whig Party. The term "Jacksonian democracy" was in active use by the 1830s.The Providence (Rhode Island) Patriot August 25, 1839, stated: "The state of things in Kentucky..is quite as favorable to the cause of Jacksonian democracy." cited in "Jacksonian democracy", Oxford English Dictionary (2019)

Second Party System: Democrat Hegemony

Many historians and political scientists use "Second Party System" to describe American politics between the mid-1820s until the mid-1850s. The system was demonstrated by rapidly rising levels of voter interest (with high election day turnouts), rallies, partisan newspapers, and high degrees of personal loyalty to parties. It was in full swing with the 1828 United States presidential election, since the Federalists shrank to a few isolated strongholds and the Democratic-Republicans lost unity during the buildup to the American Civil War.William G. Shade, "The Second Party System" in Paul Kleppner, et al. Evolution of American Electoral Systems (1983) pp 77–112.

This party system marked the first in a series of political realignments, a process in which a prominent third party coalition, often one that wins >10% of the popular vote in multiple states in a presidential election, realigns into one of the major parties, allowing that major party to dominate the federal government and/or presidency for the following decades. The first and most significant Second Party System realignment was a realignment of the differing factions of the Democratic-Republican Party of the more slave sparse Southern areas and the non-coastal Northern counties, particularly those factions that voted for Andrew Jackson, Henry Clay and William H. Crawford, into the new Jacksonian/Democratic Party.

The opposition, leftover Federalist-aligned voters who formed the Clay and Adams factions in the Coastal North, realigned into the National Republican Party in 1828. This northern base, alongside the wealthy slave owners of the dense Southern slave centers and the Anti-Masons in Vermont, Massachusetts, Northern New York state and Southern Pennsylvania, realigned into the newly formed Whig Party in 1836. With the fall of the Whig Party in 1856, the remaining Whig coalition (those not effected by the Free Soil movement in New England and the Great Lakes Region) realigned into the Know Nothing ticket that same year then realigned into the Constitutional Union Party in 1860 at the start of the next party system.

The political party system of the United States was dominated by two major parties: The Jacksonian Democrats led by Andrew Jackson. The Jacksonian Democrats stood for the "sovereignty of the people" as expressed in popular demonstrations, constitutional conventions, and majority rule as a general principle of governing, The Whig Party, assembled by Henry Clay from the National Republicans and from other opponents of Jackson. Whigs advocated the rule of law, written and unchanging constitutions, public investment of infrastructure and education, and protections for minority interests against majority tyranny.Frank Towers, "Mobtown's Impact on the Study of Urban Politics in the Early Republic.". Maryland Historical Magazine 107 (Winter 2012) pp: 469–75, p 472, citing Robert E, Shalhope, The Baltimore Bank Riot: Political Upheaval in Antebellum Maryland (2009) p. 147

After taking office in 1829, President Andrew Jackson restructured a number of federal institutions. Jackson's professed philosophy became the nation's dominant political worldview for the remainder of the 1830s, helping his vice president (Martin Van Buren) secure election in the presidential election of 1836. In the presidential election of 1840, the "Whig Party" had its first national victory with the election of General William Henry Harrison, but he died shortly after assuming office in 1841. John Tyler (a self-proclaimed "Democrat") succeeded Harrison, as the first Vice President of the United States to ascend to the presidency via death of the incumbent.

Minor parties of the era included:

the Anti-Masonic Party, an important innovator from 1827 to 1834 the abolitionist Liberty Party in the 1840s. the anti-slavery expansion Free Soil Party in 1848 and 1852.

Third Party System: Republican Hegemony

The "Third Party System" refers to the period which came into focus in the 1850s (during the leadup to the American Civil War) and ended in the 1890s. The issues of focus during this time: Slavery, the civil war, Reconstruction, race, and monetary issues.