With Hillary Clinton’s strong performance on Tuesday night, the Democratic primaries are effectively over. Barring an unforeseen catastrophe, Clinton will be the Democratic nominee. And it’s increasingly likely that her opponent will be Donald Trump, who won a clean sweep of five states on Tuesday and only seems to be getting stronger. Both parties must now gear themselves for a Clinton-Trump match-up in the fall.

Clinton indicated as much in her victory speech last night. As in earlier speeches, she made a play of Trump’s name and his penchant for racism, declaring, “Love trumps hate.” This slogan is an early clue as to how Clinton will frame the election, presenting herself as an inclusive advocate of national unity and Trump as an avatar of prejudice and divisiveness. Yet such an election poses unique problems that go beyond normal politics, and Clinton’s team may not yet appreciate how difficult this fight will be.

If winning the presidential election were all that mattered, Trump would be Clinton’s dream opponent. The Democratic front-runner struggles with poor approval ratings—55.6 percent unfavorable, according to Huffington Post’s aggregation of the polls—which means she needs to compete against someone who is even less popular than her. Trump fits that bill handsomely, standing at 63.6 percent unfavorability. Furthermore, Trump’s racism and misogyny are likely to motivate the very voters that Clinton most needs to attract: people of color, single women, and young people. And not surprisingly, in head-to-head polls, Clinton enjoys a hefty lead over Trump, even as she trails behind the less-polarizing John Kasich and enjoys a significantly smaller lead (of roughly 5 percentage points) over Ted Cruz.

If winning the presidential election were all that mattered, Trump would be Clinton’s dream opponent.

Yet there are reasons why the real estate mogul should be a far greater cause for fear than Cruz or Kasich. Cruz might be a political extremist, further to the right than any serious presidential candidate since at least Barry Goldwater. But the Texas senator is still bound by the rules of normal politics, still beholden to donors and constituencies that serve as a check on what he can say or do. Cruz would be a predictable opponent in that he’d follow a hyper-conservative script and make largely ideological arguments. Trump, in contrast, is not predictable in that manner and has no loyalty to traditional Republican causes. He could, as he has in the primaries, present himself as an opponent of the Iraq War and interventionism, a supporter of Planned Parenthood in non-abortion funding, an enemy of free trade pacts, and a defender of Social Security and Medicare.

And Trump’s unpredictability goes far beyond policy. He is wealthy enough not to worry about donors, and his core supporters have shown every sign that they will stick with him no matter what. Rather than being repulsed by his excesses, they thrill at Trump’s subversion of the rules of political decorum. This makes Trump a potentially more destructive opponent on a personal level, because he could do considerable reputational damage to his Democratic opponent.