At what point does criticism of a sitting government become the "trendy" thing to do?

So many Tories on here will have the smile wiped off there face when the election day comes. How can toff Cameron relate to people in inner city Britain? We all know his party can't win in Manchester, Birmingham, Sheffield, Liverpool, Leeds, Newcastle, Glasgow, Edinburgh, Cardiff, Swansea - many of these are places where Thatcher used to win seats. You can't get a majority without at least some of them!