Rogin, who was live tweeting the Funniest Celebrity in Washington D.C. Contest, said he was struck by the comedian in the face.
He was allegedly punched three times.
Police were called over the alleged assault.
Before Rogin was punched, he wrote a critique of Nainan's jokes.
CNN's Candy Crowley was also at the competition.
And Ralph Nader, who Rogin said opened, "by saying he isn't funny and proceeds to live up to his word."
Police later arrived at the scene:
Nainan reportedly was arrested after the incident.
Rogin said he was fine, and implied the attack was sparked by his tweets.
Eli Lake, senior national security reporter for Daily Beast, tweeted he spoke with Rogin after the incident.
Update — Sept. 25, 2013, 12:40 p.m. ET:
Rogin described the incident to The Washington Post:
"He said, 'Are you Josh Rogin?' I said yes, and he punched me in the jaw."
Nainan also pushed him, Rogin said, then briefly walked away – only to return to take two more swings. (One connected, Rogin said.)
Rogin said he was surprised by the attack. "I didn't think I was being too harsh with him – he's a professional comedian and I was being a professional journalist."
Also: "My face hurts."
Michelle Broder Van Dyke is a reporter and night editor for BuzzFeed News and is based in Hawaii.
Contact Michelle Broder Van Dyke at firstname.lastname@example.org.
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