David Cameron has been desperate to find a 'clause 4' cause, and he seems to have decided that grammar schools are it! It is an unusual situation for a public school educated leader to be in, but it is understandable in the context of the political strategy of 'triangulation'. Cameron's assumption will be that in order to make the Tories more electable, he needs to ditch some of the more obvious right-wing policies and rhetoric once employed by them. This is basically the policy followed by Clinton in America and Blair here - that public perception has to be challenged as radically as possible, which may mean sharp shifts away from previous perceived positions.
The real question for Cameron is whether he is right in assuming that grammar schools were an alienating part of previous Tory policy. It seems unlikely. In non-grammar school areas, voters are not likely to give it much thought, other than perhaps to reflect on how it wouldn't be a bad idea! In grammar school areas there is, of course, a huge level of support for the remaining state system that still produces good results. What Cameron has done, of course, is to generate massive dissent within his own party, which he may consider to be good of itself, since it allows him to show that he does represent a radical change from previous Tory leaders who were too identified with their grassroots' attitudes and ideas. The downside for him, surely, is that too much dissent might cause a wavering in the commitment of the activists to go and and support him and his candidates; and at the moment it risks bringing adverse publicity to the Tory Party in terms of stories about 'division' - something Cameron had until now been extremely effective in dispelling.
The long-term benefits of his political move remain to be seen. What is not in doubt is that the policy itself is bankrupt and flawed; it is an unusual approach that says the existing grammar schools are doing a good job and can stay, but no-one else can benefit from them. It is even more unusual to effectively become the cheerleaders for one of the government's own, and less obviously successful policies!
More on this later I suspect. Meanwhile, for a sense of grassroots Tory anger, go to the Conservative Home site, and check the message threads.