Two weeks ago Dave’s key defence against Tory plotters, his relative popularity compared to the party, was wobbling. Today Peter Kellner has some figures that will have Downing Street breathing a collective sigh of relief. Ed is less popular than Labour, somehow Clegg is less popular than the LibDems, though Cameron is again preferred to his party. Kellner says this is the graph that shows the Tories will lose in 2015 if they ditch Dave…