Mayor Byron W. Brown will officially announce his bid for a third term Saturday at the Rev. B.W. Smith Family Life Center in downtown Buffalo, according to a source close to the campaign.

The 10 a.m. event will launch what is currently a one-man field of Democratic candidates, because nobody else has yet made the formal commitment.

But former Buffalo FBI head Bernard Tolbert remains interested, and according to several friends and associates who spoke to The Buffalo News, has told them he will run.

Some observers say a Tolbert candidacy also could entice Comptroller Mark J.F. Schroeder into the race. Though he has not taken any formal or informal steps toward running this year, the comptroller has said nothing to dampen continuing speculation about his plans.

The source familiar with the mayor’s plans, who asked not to be identified, said a strong contingent of Brown supporters is expected to be on hand for the announcement Saturday. Brown also will seek the endorsement of the Erie County Democratic Party, despite strained relations in recent years under former Chairman Leonard R. Lenihan.

New Chairman Jeremy J. Zellner has indicated his willingness to support Brown this year, but has said he expects the mayor and his political team to also back party-endorsed candidates in return.

Brown enters the race as a strong favorite. He has built a $1.1 million campaign treasury and will enjoy several advantages of incumbency such as an experienced political organization to work on his behalf. At this point, he is also expected to garner support of the Conservatives – the top minor party on the ballot.

Republican Sergio R. Rodriguez already has announced his candidacy, viewed by most as an uphill effort in heavily Democratic Buffalo.