Who votes? How are they represented? What should be the scope and scale of government? Who pays taxes and how do they affect the distribution of wealth and power? These four questions will drive the long march to the 2020 election as the nation grapples with new voter suppression laws, redistricting campaigns and, for Democrats, the platforms of over two dozen presidential contenders who promise to combat economic inequality, meet the challenges of mass immigration and reduce the insidious influence of big money in American politics.

But these are not simply questions for the 21st century. They also comprise some of the most fundamental — and enduring questions — in the history of American democracy. In fact, over a century ago, as the country wrestled with similar questions, a dramatic series of constitutional and legal innovations between 1911 and 1920 transformed the structure and content of American public life. Together they redrew the playing field of American politics. And to a large extent, Americans are still playing by those rules.

The stunning decade of constitutional change began with the admission of two new states, New Mexico and Arizona. When they joined the union as the 47th and 48th states, they sent the 434th and 435th members to the House of Representatives and launched a still-ongoing debate about reapportioning congressional representation among the states and drawing congressional district lines within them. Although disputes over gerrymandering may trace back to the early Republic, the federal Congress had added members nearly every decade for a century so that reapportionment always involved the allocation of more seats, rather than a redistribution of them and states losing House members. After 1912, however, it became a zero-sum game with Congress refusing to add seats after the 1920 census and formally capping the number of House members at 435 in 1929.

The precedent-defying refusal to add seats in 1920 especially mattered because between 1910 and 1920, the urban population had grown by 19 million people while rural areas actually shrank by 5 million.

To keep with its practice of adding seats and preventing states from losing congressional seats after 1920, however, Congress would have had to add an unwieldy 50 new members. But if the House remained at 435, a dozen states would lose seats and power would swing from the South and Midwest to the urban Northeast. Since that threatened both the Republican majority and the power of southern Democrats, the GOP and a handful of the southerners stonewalled for a decade before finally conceding, and allowing the House to be capped at 435 seats.

With three times as many Americans today as in 1911, that decision creates huge districts of widely varying size. Representatives have therefore become more reliant on lobbyists and large contributors, less responsive to constituents and inimical to the democratic principle of one person, one vote.

In 1913, a year after admitting New Mexico and Arizona, the states ratified both the 16th and 17th amendments. The latter had an immediate impact, providing for the direct election of senators rather than selection by state legislatures — an effort both to combat political machine power over the electoral process and to prevent long vacancies caused when different parties controlled the two houses of a state legislature. The amendment cured the vacancy problem and ended the practice of bribing state legislators to gain their support for Senate, but it failed to fulfill reformers’ hopes that the Senate would become less of a “millionaire’s club” susceptible to the influence of special interests.

The former — the income tax amendment — did not have such an obvious immediate impact because initially so few Americans would be subject to the tax, and even fewer subject to state income taxes. But in the long term, it transformed the fiscal basis of American governance from regressive taxes on goods to progressive levies on income and wealth. Almost overnight, this amendment transformed the source of revenue for federal government. In 1910, customs duties accounted for nearly half of all federal government receipts, with alcohol and tobacco taxes making up another 39 percent. A decade later, the income tax furnished the majority of federal revenue.

This fiscal revolution facilitated fundamental changes in the size, scope and purposes of government. It allowed for the funding of a wide range of public goods and services and regulatory agencies to oversee them. It also required the development of an administrative capacity to track income, profits and inheritances, which meant gathering a lot more information about people’s economic lives. In short, it underwrote the subsequent expansion of the modern American state.

Next, in January 1919, came the ratification of the 18th Amendment. Prohibition in some ways advanced the political revolution that the income tax had underwritten — the transformation in the size and scope of the federal government and its intensifying presence in the lives of ordinary American citizens. While 19th-century Americans little felt the direct hand of the national government in their daily lives, Prohibition expanded federal power, affecting the livelihoods of many and the leisure pursuits of many more.

But increased capacity did not accompany that greater authority. With fewer than 1,000 federal agents for the entire country, enforcement of Prohibition depended on local authorities and on private actors like the American Legion. And while this amendment was repealed in 1934, it created a model of governance that still stands today. That Prohibition model of far-reaching national involvement in the day-to-day lives of American citizens, implemented by local governments or in partnership with private actors, with dramatically varying impact on different regions and populations, can be glimpsed in efforts ranging from the Affordable Care Act to the fight against opioid addiction.

If the fixing of the House and the 16th, 17th, and 18th amendments established the structures of 20th century American governance, women’s suffrage transformed the spheres of political mobilization and electoral competition.

Millions of women voters not only enlarged the electorate, but also catalyzed major changes in the structure and style of national politics as it shifted from a time when parties oriented every aspect of political, social and cultural life — and local party organizations formed the principal intermediaries between politicians and ordinary citizens — to an era when politicians communicated with and mobilized voters primarily through mass media and organized interest groups.

Women voters, many party leaders believed, generally lacked the fierce partisan attachments that had long characterized the political lives of American men. “Unbossed, unterrified, taking their own measure of each candidate presented,” one women’s group explained, female voters would not slavishly follow party leaders, but picked “fastidiously among the lot of them, weighing qualities here and balancing defects and handicaps there.”

When the DNC’s newly created Women’s Division strategized about attracting women voters, it explicitly rejected party building. The manual it created for women campaign workers warned that “newly enfranchised” women remained “unwilling to toe themselves to the narrowness of one political party.”

Because they had been excluded from traditional party politics, women had created an alternate political universe of nonpartisan interest groups and voluntary associations, whose importance grew in the aftermath of suffrage. This then, marked a crucial milepost in the decades-long transformation from the largely face-to-face politics of parties that had dominated 19th century American elections to the mass-mediated politics of interests that emerged in force by the middle of the 20th century.

A century ago, a constitutional and legal revolution rewrote the rules of engagement for American public life, at once expanding the scope of government, accelerating the shift toward media politics and stoking the partisan gerrymandering that defines contemporary American politics. Today, as we grapple with many of the same questions, Americans once again face a dysfunctional political landscape that requires fundamental, constitutional change. That offers the best promise for reviving American democracy — but would also introduce new perils and problems that would shape politics for the rest of the 21st century.