Coventry (and Dublin, Lewisham etc) is or was down to what
Nigel Irritable said hard work talking to people, building roots, and putting forward a platform that generally seems to match some of people's real aspirations.
In Seattle - I don't think the vote did come from nowhere - but clearly it was a massive victory that wasn't entirely down to local organising but that did play a key role among other things but what there is no evidence of is it being part of a more generalised shift towards a more combatative working class.
I appreciate that many people in the CWI like Nigel and Spiney understand what works and I do think the SP is currently the only far-left organisation with any potential at all - but there are no short cuts to building a political movement, there are no alternatives to slow and patient building of rooted effective local organisation in communities and workplaces. And I would suggest that recent British political history bares that out - from Militant in Liverpool to the IWCA to Nellist to Bob Crow and the RMT.
Even the recent history of the Labour party over the last 30 years shows...
Yes sometimes things speed up and you can build a mass movement relatively quickly but it needs a spark such as the poll tax something that is widely and deeply felt by a critical mass of people - and even then I suspect that if something like that flared up now given the relative weakness of those currents that provided influence to the poll tax movement they would not be in the same place to take advantage.