Ordinary voters seem to share this view of midterms as less important sideshows to the main events. As a result, voter turnout in midterm elections is one-quarter to one-third lower than in presidential elections.

But many midterm elections have been at least as important as the majority of our presidential elections, if not more important. In some cases, they have resulted in seminal legislation that reshaped America, and in other cases, they signaled transformations of our political parties, our governing institutions and American politics in ways that would drive political debate for decades. Indeed, what happens this year may be just as important as President Trump’s stunning rise in 2016 and whatever happens in 2020.

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In 1995, political scientist David Mayhew (full disclosure, he was my adviser in graduate school) identified what he described as “innovative” midterm elections. These elections elevated a new dominant congressional coalition that went on to have considerable success implementing a fresh agenda and remaining in power.

Mayhew identified four midterms that met these criteria:

1810, when the Jeffersonian Republican “War Hawks” who enacted a nationalist economic agenda gained power, setting the stage for the War of 1812.

1866, when, responding to white Southern intransigence after the Civil War, Radical Republicans swept to power and implemented far-reaching and egalitarian Reconstruction policies.

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1910, when Democrats gained control of Congress for the first time since 1892 and, allied with Progressive Republicans, enacted a variety of Progressive reforms over the next eight years.

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And 1938, when Democrats kept control of Congress but lost the massive majorities that enacted most of President Franklin Roosevelt’s New Deal legislation. As a result, a cross-party “Conservative Coalition” of Southern Democrats and Republicans rose to dominate Congress for the next 25 years, hamstringing progressive legislation and preventing any major extension of the New Deal until the 1960s.

Several other midterm elections failed to meet Mayhew’s criteria but had critical, if narrower, impact on public policy. In 1874, Democrats regained control of the House of Representatives for the first time since before the Civil War and ended congressional support for Reconstruction. This severely limited the Grant administration’s ability to ensure African American civil rights in the South, and left the promise of the Reconstruction constitutional amendments unfulfilled for nearly a century.

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In 1934, Democrats managed to avoid the usual pattern of midterm losses for a president’s party. In fact, they gained nine seats in both the House and the Senate. Emboldened, Roosevelt and congressional Democrats enacted an even more liberal “Second New Deal.” This included passing the Wagner Labor Relations Act and the creation of the modern welfare state, with the enactment of Social Security, unemployment insurance and Aid to Families with Dependent Children.

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All six of these elections had consequences that exceeded those of many presidential elections and reshaped politics and governance for years to come.

A second set of equally important midterm elections had less impact on policy but marked a transformation of American politics or the American party system.

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The 1826 midterms, for one, heralded the rise of a new force in politics. Following the divided and controversial election of 1824 when Andrew Jackson lost to John Quincy Adams despite winning the popular vote, the Jacksonians organized into their own party and took control of Congress. Jackson went on the win the presidency in 1828, and his new party, the Democrats, dominated American politics for the next three decades.

The party system that would emerge from the rise of the Jacksonians, which pitted the Democrats against the Whigs, collapsed in a midterm election as well. In 1854, the emergence of the nativist American Party (better known as the Know-Nothings) and the anti-slavery Republican Party led a coalition of anti-slavery advocates to overthrow the Democrats and elect a new speaker of the House. Out of this chaos, the Whig Party collapsed, the Know-Nothings faded away and the Republicans emerged as a new major party. This change also left slavery as the central fault line in American party politics, helping to precipitate the Civil War.

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While they didn’t herald the rise of new parties, several other midterms, including 1894 and 1994 — when Republicans captured control of the House of Representatives for the first time in 40 years — transformed the balance of power in American politics.

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Equally importantly, another set of midterm elections shifted the power balance within the majority party. In 1958, for example, Democrats established dominance in both houses of Congress by winning 49 House seats and 12 Senate seats. But more significant than the size of the Democratic gains was who got elected. Most of these newly elected Democrats were Northern liberals who began to shift the party away from its Southern and conservative leadership. In particular, they helped remake the Democrats as the party of civil rights.

Similarly, in 2010, the wave election that propelled Republicans to a majority in the House brought a new and more aggressive conservative politics to Washington. Not only did the Tea Party Republicans quickly dominate the GOP congressional agenda, but they presaged the rise of Donald Trump.

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These elections show that while midterm elections are often left out of the history books, they routinely have been key moments in American politics and deserve to be treated as such.

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Will 2018 be another historic midterm election? Obviously, it depends on the outcome, and even then it may be years or even decades before we will know for sure. On the other hand, this election already appears to be significant in at least one respect. This year has seen a record number of women nominated to run for Congress and, consequently, a record number of women will likely serve in the next Congress.