Those in political power rarely get to choose their visual biographer. Take President Jacob Zuma, the subject of a new exhibition in Cape Town. Speechless offers an unflattering appraisal of the Zuma years. Hosted by dealer Heidi Erdmann and jointly curated by artists Andy Mason and Su Opperman, this tart little group show centres on a singular personality: the induna of Nkandla.There he stands, fending off Julius Malema's crotch grab, in a brash painting by Themba Siwela. And there he is again, towering over an ox-wagon circle, laughing, in a watercolour by Alastair Findlay.Two works describe the urgent mood of this exhibition. Each takes its cue from recent events at the University of Cape Town.In an ink drawing by cartoonist Moray Rhoda, Zuma appraises three figures seated on a sculpture plinth. The figures, which all resemble Zuma, quote the gestures of the three wise monkeys of Toshogu Shrine, popularised in the expression "hear no evil, speak no evil, see no evil"."Heh heh," laughs Zuma as he gives them the middle finger.Veteran cartoonist Mogorosi Motshumi also shows Zuma enshrined on a plinth, albeit next to a statue of HF Verwoerd. Zuma's laughter turns to horror as he realises the approaching human figure, cap turned back, is about to spoil his effigy with poo.Chumani Maxwele, the student activist who splashed human faeces over Marion Walgate's bronze sculpture of Cecil John Rhodes earlier this year, also enjoys a walk-on role. He is posed on a stone plinth, vigorously stirring a pot of something in one of Findlay's 12-part series of watercolours.This indignant exhibition was inspired by the shambolic events that played out during the opening of parliament earlier this year. According to its curators, the show aims to visually record the "speechlessness experienced by many South Africans confronted by the current political malaise".Zuma is now a ritual subject for socially engaged artists.But does a recalcitrant figure unloved by beret-wearing Reds and the white middle-class make for good art? Only sometimes, based on this exhibition.To be fair, all the artists cleverly exploit Zuma's many traits: his stoicism, his humour, his familial allegiance, his girth and his increasingly weary look.Chip Snaddon's The Laugh (2015), a four-part charcoal and ink drawing, manages to wrest metaphor from an over-burdened subject. Moving from a tight focus on Zuma's teeth, his work jumps to a row of shack settlements.Speechless also includes work by Jonathan "Zapiro" Shapiro. It used to be that Zapiro and artist Anton Kannemeyer enjoyed near total exclusivity to Zuma's image. Where Zapiro preferred satire riffing on current news, Kannemeyer - who is not in this show - opted for cool realistic portraiture.Something shifted around 2010, when Ayanda Mabulu painted a cyborg-like study of Zuma with a strange phallic apparatus. Brett Murray's controversial 2012 painting The Spear, opened the floodgates.How will the Zuma years be remembered? On the evidence of this patchy but ultimately engaging exhibition, without much affection...