Divisions between voting groups, on both the left and right, were responsible for President Donald Trump’s surprise victory in the 2016 presidential election, a Nobel Prize-winning professor said Friday.

Eric Maskin, an Adams University professor at Harvard University who received the 2007 Nobel Prize in Economic Sciences, spoke about flaws in the current election system and how presidential elections could be improved to better represent voters.

“In the first 17 primaries and the general election alike that Trump won, the number of anti-Trump voters exceeded pro-Trump voters,” Maskin said. “And you might ask, how was this possible?”

Maskin said in every case, Trump faced multiple opponents: Florida Sen. Marco Rubio, Texas Sen. Ted Cruz, Ohio Gov. John Kasich and many more at the beginning. He said the anti-Trumps were split over all of those opponents.

“There’s reason to believe that given that extreme political figure Trump was, he might well have been defeated had that opposition coalesced into [a] single candidate,” Maskin said. “But it didn’t — there were multiple opponents, and they basically split the anti-Trump vote.”

Maskin said when Rubio and Cruz were still viable candidates, they were both more popular than Trump and could have beaten him. He said Cruz and Rubio lost to Trump because their support was divided.

“It was a similar phenomenon in the general election,” Maskin said. “In Michigan, Pennsylvania, Wisconsin, the difference between the Trump vote and the Clinton vote was smaller than the number of people in the state who voted for Jill Stein, the Green Party candidate.”

Maskin said Clinton would have won the election if Stein voters threw their support for her instead. American elections operate under the plurality rule, which means the candidate with the most votes wins.

“Vote-splitting, in this case between Clinton and Stein, was responsible for allowing Trump to win,” Maskin said. “Plurality rule has a flaw that it’s highly vulnerable to vote-splitting.”

Maskin then discussed what he thought was a better way to run presidential elections.

“One problem with the plurality rule is that it doesn’t give you very much information about what voters want,” he said. “Yes, you know who their favorite candidate is, but that may not be the only information.”

Maskin said voters should be able to provide more information during elections, like how they feel about all candidates. He said this is not possible under the plurality rule because voters are forced to choose only one candidate.

“In the 2016 Republican primaries, Rubio or Kasich might have defeated Trump one-on-one, but there was no way for determining that for sure because the information wasn’t collected,” Maskin said. “The solution is to get more information about what voters really want by ranking the candidates.”

Maskin said the solution he wanted to propose goes back well over 250 years to Marquis de Condorcet, a key figure in the French Revolution. He said Condorcet promoted what is now called a majority rule.

Maskin said the voters would submit rankings, and the winner is the candidate who ends up with the highest combined percentage of votes.

“The reason Trump wins under plurality rule is because the rest of the voters split between Rubio and Kasich,” Maskin said. “Individually, both Rubio and Kasich are more popular than Trump, but together they fail.”

Maskin said this shows that majority rule makes it possible for the election of centrist candidates even if they’re not major party candidates.

“And it may work to bring together a country that [has] been badly polarized,” he said.