Cambridge Mayor Alfred E. Vellucci is sponsoring an open forum on the steps of City Hall this afternoon, to allow all candidates for City Council and School Committee to present their political views at what he yesterday termed "an old-fashioned, name-calling, anything-goes rally."

Vellucci, who is running for re-election this year, yesterday predicted that rent control, a civilian police commissioner and condominium conversions will be among the issues raised, adding that the crowds will be able to tell for themselves which candidates are "forked-tongued."

All candidates from the Cambridge Convention '77, Independents and all other participants in next week's election are invited. He predicted that all the candidates will appear at the event.

Vellucci, who said he thinks his role as moderator at the forum will not be a conflict of interest, said he hopes to recapture the politics of "yesteryear" when "all the public forums and meetings were held in the streets, not at teas and coffee klatches."

Until about 25 years ago, candidates for local office rode around in trucks equipped with microphones, stopping at a corner or gathering place. Crowds would gather as the candidate spoke, Vellucci said, recollecting rallies that became so large the police had to come to allow traffic to pass.

Vellucci said this type of rally, scheduled for 4 p.m. today, is a good way for candidates to present their platforms, respond to voters and present their perceptions of the issues.