Hillary Clinton’s lead in the popular vote is growing. She is roughly 30,000 votes behind Donald J. Trump in the key swing states of Michigan and Wisconsin — a combined gap that is narrowing. Her impassioned supporters are now urging her to challenge the results in those two states and Pennsylvania, grasping at the last straws to reverse Mr. Trump’s decisive majority in the Electoral College.

In recent days, they have seized on a report by a respected computer scientist and other experts suggesting that Michigan, Pennsylvania and Wisconsin, the keys to Mr. Trump’s Electoral College victory, need to manually review paper ballots to assure the election was not hacked.

“Were this year’s deviations from pre-election polls the results of a cyberattack?” J. Alex Halderman, a computer science professor at the University of Michigan who has studied the vulnerabilities of election systems at length, wrote on Medium on Wednesday as the calls based on his conclusions mounted. “Probably not.”

More likely, he wrote, pre-election polls were “systematically wrong.” But the only way to resolve the lingering questions would be to examine “paper ballots and voting equipment in critical states,” he wrote.