Nigel Farage had milkshake thrown at him during a campaign walkabout.
The Brexit Party leader had just given a short speech in Newcastle as part of a tour of the country ahead of the European elections.
A man was dragged away by a police community support officer and later seen in handcuffs.
Paul Crowther, 32, from Throckley, Newcastle, said it was a £5.25 Five Guys banana and salted caramel milkshake.
Mr Farage was campaigning in the North East ahead of polling day on Thursday.
A Northumbria Police spokesperson said: "A 32-year-old man has been arrested on suspicion of common assault and remains in police custody."
Mr Crowther said: "I didn't know he [Mr Farage] was in town, I thought this is my only chance.
"It's a right of protest against people like him.
"The bile and the racism he spouts out in this country is far more damaging than a bit of milkshake to his front."
Standing in handcuffs outside a branch of Waterstones, Mr Crowther said he did not regret his actions.
He denied an allegation that someone was cut, saying he only threw liquid on the politician.
Of his milkshake, he added: "I was quite looking forward to it, but I think it went on a better purpose."
Mr Farage is the the latest victim of a protest which has seen other European election candidates such as Ukip's Carl Benjamin and ex-English Defence League leader Tommy Robinson suffer similar attacks.
He was heard to comment "complete failure... I could have spotted that a mile off" and "how did you not stop that?"as he was ushered away by his security staff.
One of his team was also heard to say "sorry" as Mr Farage was walked to his taxi and then driven away from the event, where he had met voters by the city's Grey's Monument.
He later tweeted: "Sadly some remainers have become radicalised, to the extent that normal campaigning is becoming impossible.
"For a civilised democracy to work you need the losers' consent, politicians not accepting the referendum result have led us to this."