When a distraught constituent accosted her on Tuesday night at a restaurant in the nation’s capital, Representative Nancy Mace confronted an impossible task that sprang from President Trump’s false promises: getting them to understand why she and other Republicans in Congress could not simply overturn the results of the election.

Driven by Mr. Trump’s fictitious claims that the election had been stolen from him — and that lawmakers and Vice President Mike Pence could clinch him another four years in power during Congress’s official electoral count — the voter had come all the way from Ms. Mace’s home state of South Carolina to witness it. Now, the voter, shaking and in tears, demanded to know why Ms. Mace, a first-term congresswoman, had refused to join the effort…

“It didn’t matter what I said,” Ms. Mace said in an interview. “They didn’t believe it.”…

“Their hearts, minds and wallets were taken advantage of,” Ms. Mace said, her voice rising in fury. “Millions of people across the country who were lied to. These individuals, these hardworking Americans truly believe that the Congress can overturn the Electoral College.”