Chris Millman, 60, was allegedly flung over a bike stand by the station’s rear entrance at about 6.30pm on May 23, the day of the European Elections.
He reported it to Avon and Somerset Police the following day. He told officers he was handing out leaflets when a man grabbed him by the jacket and threw him to the ground, causing a small cut to his finger.
Bristol Live published an appeal for information about the incident, which led a man to speak to police.
An Avon and Somerset Constabulary spokeswoman said: “A man came forward on June 3, having seen the appeal on Bristol Live.
“He is due to be interviewed voluntarily on June 14.”
A witness to the incident told Bristol Live Mr Millman was “basically rugby-tackled” and flung over a bike stand.
Anyone who witnessed the incident or who has any other information which could help the police investigation is asked to get in touch through www.avonandsomerset.police.uk/contact or by calling 101, quoting reference 5219115023.
Alternatively contact the independent charity Crimestoppers on 0800 555 111. They never ask your name or trace your call.