In an interview on the sidelines of the party retreat, her reinvention was on vivid display. Ms. Stefanik repeated Mr. Trump’s lies about the 2020 election being stolen and refused to acknowledge Mr. Biden as the legitimately elected president.

“Joe Biden is in the White House right now — the American people understand that — but they do have questions,” she said in between a lunch with former Secretary of State Condoleezza Rice and a dinner with the author of a book called “Woke, Inc.”

“In my district, I still get questions about it,” Ms. Stefanik said, adding, “I think there are constitutional questions on the unconstitutional overreach of unelected individuals in states like Pennsylvania.”

And as her party veers toward extremism, Ms. Stefanik refused to condemn the Republicans who speak most loudly to the fringe. Asked about Ms. Greene, who recently spoke at a white nationalist event, and Representative Madison Cawthorn of North Carolina, who has called President Volodymyr Zelensky of Ukraine a “thug,” she said the two were merely reflecting the views of the voters in their districts.