Physicist Stephen Hawking slammed Donald TrumpDonald John TrumpWarren: Dershowitz presentation 'nonsensical,' 'could not follow it' Bolton told Barr he was concerned Trump did favors for autocrats: report Dershowitz: Bolton allegations would not constitute impeachable offense MORE on Monday and questioned how the presumptive GOP presidential nominee was so popular.

Hawking called Trump a "demagogue who seems to appeal to the lowest common denominator" during an interview on the United Kingdom's ITV morning show, according to The Associated Press.

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Hawking said he was baffled by how Trump had made it so far.

"I can't," Hawking said when asked to explain why Trump was so popular.

Last week, Trump secured the number of delegates necessary to clinch the Republican nomination.

Trump has been the only candidate left in the GOP race since rivals Ted CruzRafael (Ted) Edward CruzRepublicans show little enthusiasm for impeachment witness swap Texas House special election to gauge suburban mood Texas Democrats roll out plan to win state House in November MORE and John Kasich dropped out earlier this month.

During the interview, Hawking also said British voters should be in favor of keeping the U.K. in the European union, as it helps provide support for British scientific research, the economy and security.

"Gone are the days we could stand on our own against the world,” he said.

“We need to be part of a larger group of nations, both for our security and our trade."