A new political ad by Republican Congressman Duncan Hunter is being labeled racist and un-American.

The ad, already shared on Twitter more than 1,000 times, attacks Democrat Ammar Campa-Najjar, who is challenging Hunter for his seat in the House of Representatives.

"Ammar Campa-Najjar is working to infiltrate Congress. He's used three different names to hide his family's ties to terrorism," the ad says, saying Campa-Najjar is being funded by the Muslim Brotherhood. "...A Palestinian, Mexican-American Democrat named Ammar Campa-Najjar doesn't get his support from the people of San Diego."

The ad centers around Campa-Najjar's grandfather, a mastermind of the 1972 Munich massacre, which killed 11 Israeli athletes. Campa-Najjar says his grandfather died 20 years before he was born and disavows him. The ad also quotes Campa-Najjar's father supporting the attack, which Campa-Najjar says is patently false.

"It is just so dishonorable, so dishonest, and I think the fact that Congressman Hunter is spending to say my name tells you that he is terrified," said Campa-Najjar, who describes himself as a devout Christian.

Campa-Najjar added he had a federal security clearance during his time working for the government.

Congressman Hunter and his wife Margaret are facing 60 counts of campaign fraud. They pleaded not guilty in Federal court last month. Still, the most recent 10News scientific poll shows him holding a lead over Campa-Najjar.

But Thad Kousser, a UCSD Political Scientist, said the personal attacks show Hunter takes Campa-Najjar as a serious threat.

"Both sides are going negative on each other, but I think an advertisement that questions someone's loyalty to the country based primarily on their ethnic heritage and heredity - there's something un-American about that," he said.

A call and email to Hunter's spokesman was not immediately returned.