Léger has a poll on the federal political scene in Quebec and it contains questions on the NDP leadership race. (document in English)
http://www.leger360.com/admin/upload/publi_pdf/Politics%20in%20Quebec_August%202017%20-%20EN-FED.pdf25% are interested in the NDP leadership race. (46% of non francophones, 20% of francophones)
Considering the level of interest I don't know if other questions are meaningful.
Which candidate is preferes for next leader: Don't know 58%, None 22%
Caron 10%, Singh 4%, Angus 3%, Ashton 2%
(but Singh leads among non-franco with 8% before Caron and Ashton at 6%)
The impact of leader with turban: no effect 55%. discourage from voting 28%, encourage to vote for him 2%.
For voting intentions, Léger's question includes the name of the leader and the party.
The current situation using Mulcair's name for NDP leader is Lib 43%, NDP 19%, Bloc 19%, Conservative 15%.
NDP gets 23% of the franco vote and 9% of the non franco and by region does best outside the Quebec City and Montreal metro areas with 22%.
Using the different candidates names as leader, The Liberals gain 4% with the two frontrunners and would be at 47% while NDP gets 13% with Angus and 11% with Singh. Caron performs better with 16% (and Lib at 46%). Ashton gets 11% (Lib 46%)
So the next leader will have to get known and develop a message to attract voters.