With COVID-19 continuing to surge across the U.S., mail-in voting has become central to ensuring that voters feel safe casting ballots in November's election. But uncertainty around state preparedness ahead of Election Day has some, including elections expert Charles Stewart III, concerned.

Stewart joined Boston Public Radio on Tuesday, where he talked about strengths and weakness in voting systems across the country ahead of a pandemic-time election where, he said, “there’s an emergency everywhere."

President Donald Trump has been public in his skepticism of the legitimacy of mail-in voting. In an interview Sunday with Fox News’ Chris Wallace, he said “I think mail-in voting is going to rig the election, I really do.”

Stewart, a Kenan Sahin Distinguished Professor of Political Science at MIT, pushed back on the idea that mail-in voting itself is the issue. He expressed concern instead about how understaffed polling stations and processing hurdles could delay results, and potentially sow doubt in the public’s mind. He used New York as an example of one state that’s “massively understaffed.”

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Doubt from delayed results, Stewart warned, could inspire certain state legislatures to take drastic and worrying measures.

"What I’m worried about in the period after the election, for instance, is not Donald Trump saying ‘Oh, I was robbed.' I’m more worried about whether or not [delayed results] spurs into action the speaker of the Wisconsin State Legislature, who might be prompted to overturn a popular vote in a state and have the state legislature just elect their own slate of electors,” he said.

But he also added that Americans can trust the people tasked with counting ballots, who he said are "not the partisan hacks that many people worry that they are.”

“They’re by and large civil servants," Stewart said, "whose main instinct is to figure out a way to get everybody to vote. ... They’re running their behinds off, working really hard to recruit people, get polling places, get the mail out, get it counted, deal with whatever comes their way — ‘cause that’s just what they do.”