A man who heckled Democratic candidate for Senate Abdul El-Sayed and demanded he disavow the Muslim Brotherhood at a Michigan townhall is a former aide to the Republican senator Josh Hawley, according to congressional staff records.

At the event on Saturday, an attendee who gave his name only as “Tommy” shouted from the crowd, asking whether El-Sayed would disavow the movement. El-Sayed answered: “Sure, yeah, absolutely,” then turned the question around, asking whether the man assumed he wouldn’t.

Tommy said he had simply not heard El-Sayed reject the Muslim Brotherhood, one of the Arab world’s oldest and most influential Islamist movements. Under Trump the US has moved to designate certain chapters of the group as foreign terrorist organizations.

Over nearly five minutes at the townhall, El-Sayed pointed to how the question shouted by Tommy carried an implication of “dual loyalty”, comparing it with the doubts once raised about John F Kennedy’s Catholicism, and told the room he was running for the Senate and “happen[s] to be Muslim”.

He then asked Tommy whether he would disavow any attempt to read religious doctrine into American law. Tommy said he would not. El-Sayed answered that it was Tommy who needed to understand the Constitution, drawing cheers, and the man left the room.

The questioner has since been identified as Thomas Teepell, whose staff records show he joined Hawley’s office as an intern in 2023 and rose to operations director before leaving in February. He then became political director for Philip Sarnecki’s Kansas gubernatorial campaign, which Sarnecki then lost the Republican primary on 4 August.

Teepell is the son of the Republican strategist Timmy Teepell, a longtime adviser to Hawley and the former Louisiana governor Bobby Jindal. The Handbasket first reported the identification.

The question echoes a line of attack that Republicans have tried to push against El-Sayed for weeks, including when Rogers raised alleged Brotherhood ties during one of their debates.

After El-Sayed told NBC’s Meet the Press that neither he nor his family had any such ties, the conservative Washington Free Beacon resurfaced social media posts by his half-sister, the University of Chicago professor Eman Abdelhadi, describing their mother’s activism in the group in the 1970s. There is no evidence El-Sayed was personally involved; he was born in the 1980s and was not raised by his birth mother. He has called the suggestion that anyone in his family took part “an insane thing to assume”.

On Meet the Press, he said Rogers had raised the issue because he “really wanted to repeat the word Muslim”. In a separate NBC interview, he dismissed the questions as “not serious”.

Trump has gone further, similarly without evidence, saying at a White House lunch that El-Sayed is “100%” Muslim Brotherhood and calling him a “fraud”, and describing him on another occasion as a “member” of the group. Ahead of the weekend, Trump dog-whistled on his Islamophobia, saying El-Sayed’s name is “Adulbabababababa Mohammed El-Sayed.” He added: “So I was right. He’s a jihadist.”

The attacks come in a close race. El-Sayed holds a narrow lead in the RealClearPolitics average, 48.1% to 45.5% for Rogers. The most recent survey, from InsiderAdvantage taken on 9-10 October, had him ahead 48% to 46%. Most leads sit within or near the margin of error.

El-Sayed will campaign with Barack Obama in Detroit on Saturday 24 October, the first day of in-person early voting, at a rally that will also feature the Democratic gubernatorial nominee, Jocelyn Benson. Election day is 3 November.