Here's an encouraging Harris-Decima poll for Greens: 40% of BCians, 49% of Libs and 53% of NDPers want to see May in the next Parliament. What does this mean?
For one thing, since this question isn't asked regularly, we don't know if this represents an increase or a decrease. I would interpret the result as follows: at most half of Liberal and NDP voters would switch their vote to the Green Party if May ran in their riding.
Greg Morrow at democraticSPACE has an excellent post about projecting the outcome in Saanich--Gulf Islands. Since that post, the polling in BC has worsened a bit for the Tories, and improved for the NDP. Also, I'd be a bit kinder to the Liberals at the expense of the NDP in that riding: some NDPers that switched over to the Liberal Party last time might decide to stick around. So if Elizabeth May weren't running in the riding, I'd say that things there now stand at about CPC 34, LPC 26, NDP 22, GPC 17.
If May indeed manages to draw half of LPC and NDP voters, she'd win. But of course, that's a bit unrealistic. My own very unscientific guesswork for Central Nova suggests that May drew 40% of NDP voters there in the last election. If she manages to draw 40% of Dippers and 35% of Grits this time around, she'd end up basically tied with Gary Lunn.
However, Greg Morrow, who has been involved with the Green Party and studied these issues more carefully, seems to think that May will only draw 25% of NDPers and 10% of Grits. The prognosis for May in that case is rather poor. This estimate is partly based on the fact that Ed Broadbent got an 8% bump in Ottawa Centre. I would venture that as a current party leader, May has more pull than Broadbent.
In summary, if May can "max out" and pull 50% of Liberals and Dippers, she has a good chance of winning. If she can only get 20% of them, it'll be a hard slug. For my projections, until a riding-specific poll comes out, I will use a proportion of 30% - somewhere between Greg Morrow's model and my back-of-the-envelope calculations. Currently, that's not enough for May to win, but she's close!
Also, Harris-Decima just put out a national poll (8/13-23, 2000+ respondents) today, but full details aren't available yet. From what I was able to glean from news websites, the headline numbers are: LIB 32, CON 31, NDP 16, GRN 11, BQ 9. In Québec, the breakdown is: BQ 37, LIB 28, CON 12, NDP 11, GRN 10. Unfortunately, I haven't been able to find the all-important Ontario breakdown... Hopefully, Harris-Decima will soon post the full results (or maybe the Canadian Press will decide to write a more detailed article on the poll), so that the projection can be updated. But at first glance, this poll might be the first indication that the recent Ipsos is indeed an outlier - we will have a better idea when the regional breakdowns and this week's EKOS become available.