Three candidates gathered enough signatures by Tuesday afternoon’s filing deadline to challenge incumbent Mayor Setti Warren’s bid for a second term in office. Warren will face Ward 3 Alderman at Large Ted Hess-Mahan, public-access TV host Tom Sheff, and political activist Jackie Gauvreau Sequeira, according to the city clerk’s office. Gauvreau Sequeira’s nomination papers came in just under the wire; she had been working over the weekend to secure the 400 signatures needed to appear on the ballot. All signatures have been certified, City Clerk David Olson said. The official lineup on the ballot will be posted after Aug. 15, the deadline for a candidate to withdraw from the race. A preliminary election will be held Sept. 17 to narrow the mayoral field and the race for Ward 1 alderman at large to two candidates each. The general election will be held Nov. 5.