The enthusiasm gap between Clinton supporters and Trump supporters has been apparent in numerous polls for months and was underscored in a poll conducted this month by the Washington Post-ABC News. The survey found that 46 percent of Trump supporters described themselves as “very” enthusiastic about him, compared with 33 percent for Clinton.

What’s even more troubling for Clinton is that 93 percent of Trump’s supporters say they will vote for him on Nov. 8, compared with 80 percent of Clinton’s supporters.

John Hibbing, a political scientist at the University of Nebraska-Lincoln, said he sees the enthusiasm gap in his own classrooms. Many of his students had supported Bernie Sanders, the insurgent candidate from Vermont who ran a competitive campaign in the Democratic primary, and who for a time stripped the “inevitability” from Clinton’s campaign.

Some of Hibbing’s students applaud the historic nature of Clinton’s campaign but still have trouble getting revved up about the first woman ever nominated for the presidency by a major political party.

“I don’t sense that same kind of enthusiasm” as for Sanders, Hibbing said. “Certainly among my students they’re happy about the prospects of a woman president, but enthusiasm is another story.”