Lowest winning share of the vote in FPTP seats

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Toronto's had sub-20% winners in the last two municipal elections: James Pasternak in Ward 10 in 2010 (19.16%) and Christin Carmichael Greb in Ward 16 in 2014 (17.38%) (NB: Pasternak was reelected with 57.78% in 2014)

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Lowest federal result I can find is a Tory winning 22% of the vote in Verdun in 1935. They managed to win thanks to the CCF and Labour splitting the left wing vote almost evenly. More recently the Bloc won Gatineau on 29 % of the vote in 2008.

Brad Trost (C) won with 26.7% in Saskatoon-Humboldt in 2004.  (4-way split with 4 candidates getting over 20%, including Con-turned-indy incumbent Jim Pankiw.)


In 2015, the following sub-30% victors, all in Quebec thanks to Lib/NDP/Con/Bloc splitting it 4 ways:

Bernard Genereux (C), Montmagny et al, 28.99%
Karine Trudel (N), Jonquiere, 29.19%
Jean-Yves Duclos (L), Quebec, 28.90%
Brigitte Sansoucy (N), St-Hyacinthe-Bagot, 28.65%
Xavier Barsalou-Duval (B), Pierre-Boucher et al, 28.64%

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I'm not sure this is what you're looking for, but the star-studded 1977 Democratic Primary for NYC Mayor deserves an honourable mention, if nothing else; no candidate received more than 20%, or less than 10% of the vote:

Ed Koch: 19.82%
Mario Cuomo: 18.60%
Abe Beame (inc): 17.99%
Bella Abzug: 16.58%
Percy Sutton: 14.48%
Herman Badillo: 11.03%

Now, *that* was a cast of all-stars.  (And it's worth noting that frontrunner Koch won none of the boroughs--it was his strong second to Abzug in Manhattan that nailed it.)