Tories are not doing better in the marginals after all

Last month there were reports that the Tories were doing better in the most marginal seats than in the national polls. Triples all round on Conservative Home and Iain Dale's Diary.

Except the authoritative (fast becoming my 'word of the month', I know) figure of Stephan Shakespeare (co-founder of YouGov as well as J.Archer's former spokesperson) explains on Conservative Home that the optimism was based on a false interpretation of the poll, and that the Tories are doing no better or worse in the marginals:

...an analysis of the three most recent Populus polls, separating the data from just the 120 most marginal seats, painted a rather too rosy picture by wrongly suggesting a better result for the Conservatives in the seats that matter most, the 120 ‘most marginals’, prompting ConservativeHome and others to think that the targeted campaigning effort being made in marginal seats is paying dividends.

It may or may not be paying dividends – but the poll analysis provided no evidence for it. In fact, the correct interpretation of the data is that change in voting intention is exactly the same in the marginals as it is in the rest of the country. And that change is zero.