Things are heating up. As of now there are 3 declared candidates, Gaidamak, Nir Barkat (Chiloni), and Meir Porush (Aguda).
However, it looks like Aryeh Deri (former leader of Shas) may run, and that changes everything.
A little background. In the Ashkenazi Charedi world there are 2 parties, Aguda and Degel Hatorah. Aguda is Chassidic and Degel represents the Yeshivish community. Aguda and Degel generally have rotation agreements for mayor. One term Aguda one term Degel. This is what happened in Bnei Brak, Beitar and other places. This arrangement has come under fire recently as it forces highly successful mayors to abandon the job after 1 term for possibly inferior people.
In Jerusalem, before the last election Degel and Aguda signed an agreement and Lupoliansky from Degel was elected with the agreement that Aguda would put up the candidate in this election. The Aguda candidate is Meir Porush. However, Porush is not well liked by many groups in the Charedi world (especialy Degel) including many Chassidim (especially Ger). Therefore, Degel and parts of Aguda are not happy with his candidacy. Recently polls have show Nir Barkat, a chiloni candidate as trouncing Porush.
Based on the above Deri is thinking of running. he will certainly have the support of Shas and may get the support of Degel. If no one candidate gets 40% of the vote there will be a runoff. Deri believes that with 2 Haredi candidates (and the Charedi population about 40%) there is little chance of anyone getting 40% and all he would need to do is beat Porush. Then in a runoff, he would get the Charedi support by default to keep the chiloni out of office.