Looking at the London Mayoral election, the prediction markets (on Betfair) appear to be better than the research polls. BetFair has had Boris ahead of Ken since March 15th whilst the pollsters (with the exception of YouGov) have been saying it’s too close to call.
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YouGov have been consistently putting Boris ahead although they’ve been cutting his margin of late, indicating a Ken surge. This surge has been reflected on Betfair too. That said as YouGov have been backpedalling on Boris’ lead a little, (since Ken’s attacks on their online methodology and weighting of ethnic data amongst other things) the spread markets have clearly favoured Boris. Don’t blame them for back tracking a little - as it is very difficult to weight data so much to represent offline groups (and many low income Londoners or older Londoners will still be offline)..but I still think they deserve kudos for getting closest though when ICM, Ipsos - Mori et al were not nearly as close.