Party membership provides the activist lifeblood parties desperately need, however they only join if they feel a strong attachment to a party, its policies and feel that the party would be the best government for them and people like them (very simplistic but sufficient). The important point to note is that they are bound together by values, ideas and a vision: so what they stand for, how those translate to politics and finally how the values shape a programme. One gets a sense of the grassroots from their logo (below)
The whole modernisation process can attract members, as the party becomes more in touch with a wider social grouping, but can also demobilise the older or more traditional member. This has happened to New Labour post 1997, but they have also lost a lot of the newer members that joined up around 1995-7. Hence we hear of the party having a membership crisis.
Cameron is in danger of taking the Conservatives in the same direction. Public dissent over grammar schools is part of a symbolic battle between traditional Conservative policies and Cameron's modernisation. While he sees his approach as being modern Conservatism, it seems many feel he is mistranslating the party's values. The unofficial website of the party grassroots published the below dramatic graph derived from a poll to send a clear message from below to the leadership.
There is a major problem with revising, updating and modernising a party; you will propose to slaughter one sacred cow that everyone is prepared to fight for. Hence the choice is mass electorate or party and if the leader backs down the media will call it a U-turn, sign of weakness and of course failure. This narrative will play out in the Conservative party this week and in weeks and months to come. Cameron is standing firm and meeting the criticism head on, but will this incur a further dip in satisfaction? Interesting times!