During one of Sen. Bernie Sanders' (D-VT) rallies in Phoenix, Arizona, on Thursday, an attendee displayed a Nazi party flag behind the presidential candidate who is Jewish.

In what Steven Slugocki, chairman of the Maricopa County Democratic Party, is calling "absolutely abhorrent," a protester unveiled the Nazi flag with a swastika behind the senator who could potentially become the first Jewish president, The Washington Post reported. 

Cheering for Sanders was quickly refocused on booing the protester.

"It was absolutely wild," Brianna Westbrook, a national surrogate for the Sanders campaign, told The Post. "I never thought I would have seen a swastika at a political event. It's gross."

The appearance of the Nazi flag at Sanders' rally caused a social media frenzy.

Initially, Sanders didn't see the flag, but the viral videos, however, showed Sanders watching the man getting escorted out.

"Whoever it was, I think they're a little outnumbered tonight," Sanders told his supporters.

Not much is known about the protester, and it is unclear if the man is a Trump supporter who wanted to disrupt the Democratic socialist's campaign.

Westbrook said this is one of many protesters that attended the event. Other anti-Sanders protesters were seen waving Trump-inscribed banners, leading to minor fights and protestors being swiftly escorted out of the venue. 

The race is perhaps getting too heated with some supporters believing both Sanders and former Vice President Joe Biden should have Secret Service protection.

On the day of Super Tuesday, Joe's wife, Jill Biden, had to block vegan protesters who lunged at him. At the Los Angeles, California rally, Symone Sanders, Biden's senior adviser, had to take down a woman with a waist lock, as Blavity previously reported.