Liberal Leader Justin Trudeau says he will leave it to police to decide whether charges are warranted after he was pelted with gravel at a campaign stop in London, Ont. on Monday.
Trudeau says he felt the stones hit him but that he wasn't hurt.
The London stop is the latest Liberal tour event to be sidetracked by the arrival of what Trudeau called an "anti-vaxxer mob" but the first where he was physically assaulted.
Trudeau says it is "absolutely unacceptable" to throw things at a campaign rally, and that he isn't afraid for his own safety but for that of his volunteers, his security detail, or journalists covering the campaign.
Conservative Leader Erin O'Toole says there is no excuse for trying to intimidate, harass or promote violence.
NDP Leader Jagmeet Singh says the London event crossed a "clear line" by throwing rocks intending to harm someone.
Singh's campaign stops have not seen the same kind of crowds but the NDP leader is often subjected to racist insults, including from people driving by his events who hurl hateful slurs out their windows as they pass.
Both Trudeau and Singh say the anti-mask, and anti-vaccine elements stirring up trouble on the campaign trail are a loud but very small minority of Canadians.
The anti-Trudeau agitators have appeared in multiple provinces but their number has been greatest during Trudeau's events in southern Ontario.
Early on, some of the anti-Trudeau elements showed up sporting clothing affiliated with former U.S. President Donald Trump.
At an event in Bolton, Ont., on Aug. 27, which was cancelled when the RCMP determined it could not maintain security, a handful of people in the crowd were in Conservative T-shirts.
O'Toole condemned their actions and fired those volunteers from the campaign.
The latest of the events has seen the crowds dominated by people carrying campaign signs or wearing clothing for the People's Party of Canada.
