As the presidential election of 1800 approached, Americans were more divided than ever before. The incumbent President John Adams faced off against Vice President Thomas Jefferson, the former secretary of state and author of the Declaration of Independence.

To Jefferson and his supporters in the rising Democratic-Republican (or Republican) opposition, building the strong national government favored by Adams’s Federalist Party meant trampling on the rights of states and individuals, and destroying the revolutionary freedom on which the nation had been founded.

At the time, there was no popular vote, and no separate ballots for presidential and vice presidential candidates. Electors from each of the 16 states in the Union each cast two votes; the candidate who received the most votes became president, while the runner-up became vice president. This undeniably flawed system had led to Jefferson becoming Adams’s VP in 1796, after losing the nation’s first contested presidential race by just three electoral votes.

The 1800 election—a drawn-out battle between two starkly different visions of America’s future—would cause an outright constitutional crisis.

Voting in 1800 took place over a period of months, and the campaign, which was largely fought in the nation’s partisan press, got really nasty. Republican newspaper editor James Callender notoriously accused Adams of having a “hideous hermaphroditical character,” while a Federalist writer named “Burleigh” claimed that if Jefferson won, “murder, robbery, rape, adultery, and incest, will openly be taught and practiced.”

By mid-December 1800, it was clear Jefferson and his running mate, Aaron Burr, had beaten out the Federalist ticket of Adams and Charles Cotesworth Pinckney. But there was a problem: At least one Republican elector had been expected to withhold his vote from Burr to allow Jefferson to come out ahead. None of them did, and each man had received exactly 73 electoral votes.

The tie sent the election to the lame-duck House of Representatives, where Federalists dominated. Though public opinion favored Jefferson, many Federalists decided to throw their support to Burr, hoping to keep Jefferson from the nation’s highest office. Burr refused to confirm that he would turn down the presidency if the House voted in his favor, leading some people to conclude that he was secretly angling for the job.

Alexander Hamilton was one of these people. Though he disagreed with Jefferson on nearly every political issue, he thought Burr had few principles beyond his own ambition. In a fierce letter-writing campaign that would continue from mid-December through late January 1801, Hamilton worked hard to convince his fellow Federalists of this fact.

“There is no doubt, but that, upon every virtuous and prudent calculation, Jefferson is to be preferred," he wrote to Oliver Wolcott Jr. on December 16. “He is by far not so dangerous a man and he has pretensions to character.”

But Hamilton had lost much of his influence among fellow Federalists due to his vicious attacks on Adams (as well as a scandal in his personal life). By the time, the House began voting on February 11, 1801, Hamilton’s concerns about Burr had failed to sway many members of his party.

The Constitution mandated that each state’s delegation in the House vote as a single bloc to decide the election. This put a great deal of power in the hands of one man: Delaware Federalist James A. Bayard, who was the lone representative of his state in 1800. If Bayard changed his vote, his state changed its vote.

In the first ballot—and the 34 that followed over the next five days—Bayard cast Delaware’s vote for Burr, giving him six states to Jefferson’s eight. The delegations from Vermont and Maryland were split evenly, so they didn’t vote.

With no clear winner emerging, the nation hovered on the brink of chaos. Republican newspapers fanned the flames by suggesting possible military intervention and groups of unofficial Republican and Federalist militia began to drill in preparation for a potential civil war.

Meanwhile, Bayard (possibly due to the influence of Hamilton, who had written to him on January 16 arguing that Burr was a “man of extreme & irregular ambition”) was reconsidering his position. According to historian Ron Chernow, Bayard suggested in a caucus that he might vote for Jefferson to prevent a constitutional crisis. After other Federalists shouted him down with cries of “Deserter!”

Bayard met with two of Jefferson’s friends, John Nicholas of Virginia and Samuel Smith of Maryland. He sought to confirm that as president, Jefferson would leave certain Federalist policies, including Hamilton’s financial system, and officeholders in place.

After getting tacit assurance that Jefferson was in agreement with these terms, Bayard submitted a blank ballot during the 36th round of voting, on February 17, 1801. Federalists also stepped aside in Vermont and Maryland, allowing those state delegations to vote for Jefferson and sealing his victory, just two weeks before Inauguration Day.

Jefferson later wrote that his victory in 1800 was “as real a revolution in the principles of our government as that of 76 was in its form.” Federalists would never win another presidential race, and by 1815 had ceased to exist as a party. With Republicans firmly in control of the government, the 12th Amendment was passed by the end of Jefferson’s first term, amending the electoral process and separating the election of president and vice president.

The election of 1800 figures prominently in Lin-Manuel Miranda’s hit musical Hamilton, serving as the catalyst for the fatal clash between Hamilton and Burr in 1804. In real life, the sequence of events was more complicated, but the fallout from 1800 certainly played a significant role in the two men’s lives.

Hamilton’s stature within his party declined further after Jefferson’s election, even as Federalism itself lost influence. Meanwhile, after Jefferson declined to give his new VP any influence in his administration, and dropped him from the ticket in the next election, Burr ran unsuccessfully for governor of New York.

When rumors reached Burr that Hamilton had spoken out against him during that campaign, the long-simmering tensions between them escalated, culminating in the duel that killed Hamilton in July 1804.