Assassination attempts, fortunately, have figured in only a handful of America’s 60 presidential election years. Decisions by sitting presidents—Lyndon Johnson in 1968 and now Joe Biden—not to seek reelection after the voting had begun have happened in only two White House campaign seasons.

We Americans also haven’t seen many instances in which a former president tries to reclaim the Oval Office after leaving or losing it. In the 19^th century, Millard Fillmore and Ulysses S. Grant launched doomed campaigns. Grover Cleveland was more successful, winning a rematch with Benjamin Harrison in 1892. In the 20^th century, Theodore Roosevelt also attempted and failed, even though he led the most successful third-party challenge in our nation’s annals.

Now, of course, Donald Trump wants to recapture the White House after the nation’s voters rejected him four years ago.

Women have been major-party presidential candidates in two election years—2016 and this one—thus far. Democrat Hillary Clinton lost eight years ago to Trump. Vice President Kamala Harris, the presumptive Democratic nominee now that Biden has left the race, faces off against Trump this year.

Harris’s candidacy also marks only the third time a Black citizen has led a major party’s ticket. Barack Obama was the Democrats’ candidate in 2008 and 2012, defeating Republicans John McCain and Mitt Romney, respectively.

That’s a lot of rarities and anomalies to pack into one election season—enough to make campaign 2024 historic.

But the seething tensions animating this year’s political battle also soon will make it ugly.

Some of the ugliness will spring from ideological sources.

Both Trump and Harris are correct when they say this election is about different visions for the country.

The America Harris envisions is a more inclusive nation, one in which one’s race, religion, national origin, ethnicity, gender or sexual orientation does not hinder a person’s pursuit of happiness. In her American dream, America’s greatness bubbles up from the ground level.

Trump’s notions of what makes America great are different. His instincts are more autocratic. He believes the country draws strength from the top down—“I alone can fix it”—not the bottom up.

This year’s grand political debate will be the age-old one between the egalitarian and the authoritarian.

That alone is reason enough for this year’s political jousting to be fractious and mean-spirited.

But both campaigns and candidates have other motivations to fight hard without granting quarter this year.

Trump quite literally may be battling to stay out of prison.

If he wins the presidency again, he can shut down the federal prosecutions on charges that he compromised national security and attempted to overturn the 2020 presidential election by firing the special counsel. He still will face the state prosecutions of criminal conduct—in one such case, he already has been convicted on 34 charges—but a compliant U.S. Supreme Court likely will allow him as a sitting president either to delay or evade facing the consequences of his alleged lawbreaking.

Harris, on the other hand, represents constituencies—women, in particular—who have seen reproductive and other rights stripped away from them. She cannot pull any punches without betraying those constituencies.

There also are questions of campaign strategy and tactics.

Even though Trump is far from a student of political science, it cannot have escaped his notice that when voter turnout is high—as it was in 2020, when more than 155 million Americans, a record, cast ballots—he loses. When turnout is lower, as it was in 2016, he wins.

Negative campaigning tends to depress voter turnout. That will give the Trump campaign all the justification it needs to batter Harris with unflattering messaging.

But, Harris also has reason to swing back with ads that aren’t complimentary to Trump.

Trump energizes his own base like few figures in American history.

But he also arouses the opposition’s supporters like no one else.

Voters in America’s cities and suburbs do not like Donald Trump. So, to win Kamala Harris will bombard Americans with negative Trump spots designed to remind those voters of all the reasons those voters came not to care much for the former president.

This year’s presidential election will be historic regardless of who wins.

But it likely also won’t be pretty to watch.

That’s something both history and representative democracy have in common.

They aren’t for the squeamish or the faint of heart.