US President Donald Trump has accused Michigan Senate candidate Abdul El-Sayed of being a member of the Muslim Brotherhood, a claim the Democrat denies.
Mr Trump also repeatedly referred to Mr El Sayed as “Mohammed” as the race in the key battleground state heats up.
“I call him Mohammed Al Fayed. His name is Abdul, but I think I call him Mohammed Abdul El-Sayed, and he's a Muslim Brotherhood guy, 100 per cent,” he said at the White House on Thursday.
The Brotherhood accusation comes less than three weeks before the midterm elections, as the race in the swing state intensifies. Michigan is home to about 300,000 Arab Americans, and Mr Trump has won the state twice.
Polls show Mr El-Sayed narrowly ahead of his Republican opponent, Mike Rogers, an ally of Mr Trump.
Throughout the campaign, Mr Trump has referred to Mr El-Sayed as a radical and a “jihadist lunatic”, among other Islamophobic insults.
The November 3 elections will determine control of Congress, and Michigan is among the most closely watched Senate races. If Mr El-Sayed wins, he would become the first Muslim elected to the US Senate.
US media reports this week have quoted social media posts by Mr El-Sayed’s half-sister that allegedly refer to his mother as a supporter of the Muslim Brotherhood.
Mr El-Sayed, the son of Egyptian immigrants, has denied the accusations and at times dismissed them. His parents were divorced when he was a child, and he was raised by his American stepmother.
“I have no ties. We have no ties,” Mr El-Sayed said in an interview with NBC that aired on Thursday. “I have never had these conversations with my mother. I wasn’t raised by my mother.
“You’re using hearsay evidence from a tweet. It’s just not serious.”
Mr El-Sayed, an epidemiologist and former health official, has also faced questions about his credentials.
During a heated debate last week, Mr Rogers called Mr El-Sayed a “con man” and accused him of having ties to armed groups in the Middle East.
“He can't condemn Hamas. He can't condemn the Muslim Brotherhood. He says his home is Egypt,” Mr Rogers said.
He later suggested that concerns about surveillance could be personal for Mr El-Sayed because he or someone in his family might be suspected of terrorism.
“Go ahead and say it,” Mr El-Sayed interjected. “You've been tiptoeing around it the whole time.”