Candidates like Nenshi certainly have an up hill battle, but it's not impossible for them to win.
The entrance of Barb Higgins, in my view, makes it simultaneously more difficult for people like Nenshi to win, but also easier.
It's easier, because with only McIver in, the name recognition factor was held only by McIver, giving him an automatic big lead. Higgins now splits up that support substantially, bringing 3rd and 4th place candidates much closer to the plurality needed to win. It brings the races closer to them and potentially a third candidate could sneak in and win the race with 25-30% of the overall vote.
On the other hand, when it was only McIver, someone like Nenshi could position themselves as the Anti-McIver - try and make it a him-vs-me race, and build recognition as the logical alternative. With Higgins in, many people now see her as that alternative candidate - and on her own carries tremendous appeal for those that wouldn't necessarily support McIver and may have previously backed a Hehr, Nenshi or Hawkesworth.
Good blog post from calgarypolitics.com on the subject.
http://calgarypolitics.com/2010/07/2...run-for-mayor/