Donald Trump announced he was running for president in June, and pundits and rivals have been eagerly anticipating the collapse of his campaign ever since. They’re still waiting—the New York real estate developer and reality TV star has surpassed everyone’s expectations, except perhaps his own, and is now poised to win the Republican nomination.
As of today, he’s won contests in 27 states and leads Ted Cruz, his closest rival, by a considerable margin in delegates. With 992 under his belt, he’s nearing the 1,237 he needs to win the right to run against the Democratic nominee—most likely Hillary Clinton—in November’s general election.
And so the world has started to come to grips with the likelihood of a Trump nomination, and the less certain but still greater-than-zero prospects of a Trump presidency.
He faces an uphill climb, with the majority of Republicans and an overwhelming percentage of Americans against him. But assuming he wins the nomination, Trump’s bid will be ultimately decided by America’s convoluted presidential voting system, known as the electoral college.
Political forecaster Larry Sabato, director of the nonpartisan Center for Politics at the University of Virginia, puts it this way on his Crystal Ball blog: “We are going to cling to one central fact about presidential elections: The only thing that matters is accumulating a majority of 270 votes in the electoral college.”
Note the difference in expected votes for the Democratic and Republican nominees between March, 2015, when Trump’s candidacy was little more than a joke, and March, 2016, when it was clear that he was no laughing matter.
In 2015, the race was a toss-up—neither party had enough electoral college votes to win. But in 2016, with Trump the presumptive nominee, it clearly suggests a Democratic victory. In short, unless something big changes, a Trump presidency is very unlikely.
The electoral college isn’t a place—it’s a process, and a complicated one.
The system was put in place by the Founding Fathers and enshrined in the Constitution, as a compromise between a purely popular vote and a president chosen solely by legislators.
Taking cues from the Holy Roman Empire, the college currently consists of 538 electors divvied up amongst the 50 states, in proportion to the number of members in a state’s Congressional delegation (which roughly corresponds to population): one for each member in the House of Representatives, plus two for its senators.
The smallest allotment is three (for the District of Columbia and low-population states like Wyoming), and the largest is 55 (California). Territories such as Puerto Rico and Guam don’t get any votes.
Most states have “winner-take-all” rules that assigns electors based on who wins their popular election; Maine and Nebraska allocate theirs based on “proportional representation.” So the key to winning an election isn’t so much winning a majority of votes nationwide, but a sustainable number of (ideally populous) states.
The results of the electoral college usually align with the popular vote, but not always. Rutherford B. Hayes in 1876, Benjamin Harrison in 1888, and perhaps most infamously, George W. Bush in 2000 all won the presidency while receiving fewer popular votes than their opponents.
The Center for Politics predicts that, if the election were held today, the Democratic nominee would walk away with 347 electoral votes to the Republicans’ 191.
“We went ahead and gave Trump everything we could give him in the Romney regime, the deeply red states,” Sabato tells Quartz. “We took North Carolina away from him—Romney only held onto North Carolina just barely. We were very kind to Trump.”
When asked if he could foresee any situation in which Trump could possibly scratch out a victory in the electoral college, Sabato added, “It’s stretching my imagination to the breaking point. But it’s a failure of imagination to say never. It really is.”
He supposes that if Hillary Clinton were indicted over the security breach involving her emails and home server, and she refused to resign as the nominee, that might skew some votes in Trump’s favor. “The Democratic National Committee has the power to replace, but only if a nominee has resigned or died or become incapacitated,” he said.
Another possibility is that of a multi-candidate melée—“if the election really fractures,” he says. “Let’s say Bernie Sanders never reconciles himself to Hillary—which I don’t think will happen—or maybe he accepts the Green Party nomination. Then you’ve got Libertarians and the Constitution Party, and Donald Trump running as an independent because Ted Cruz took it from him. Think of 1860!”
That year’s presidential election saw Abraham Lincoln win by a slim margin over Stephen A. Douglas and John C. Breckinridge, both Democrats, who arguably lost votes to Constitutional Party candidate John Bell.
“It can happen that way. You can have someone elected with well under 50% of the vote if the electorate is fractured enough,” Sabato explains. He’s confident, however, that any such splintering will be minimal.
“We live in such a polarized era,” he says, predicting that most Republicans will fall in line behind Trump, and most Sanders supporters will eventually unite around Clinton. “They’ll look at the other side and say, ‘God I hate X.’”