In Totnes, the Tory majority is less than 2,000. But by holding an open primary, the Tories have created a situation where one in four voters has been involved in the selection of their candidate. This must give the Tory candidate a significant head-start in terms of both name recognition and people feeling connected to them.
I suspect that the success of the Totnes experiment means that the Tories will use open primaries in a slew of the other seats where they have yet to select a candidate.
PS Matthew Parris was the moderator for the hustings in Totnes and his thoughts on the whole process are well worth reading.