So for several reasons, this is going to be a real test of nerve for the Conservatives and Mr Cameron. They’re already getting some flack for dropping immigration (the Sun is particularly hostile today: "If he won’t address the issue of immigration, you have to wonder if he really wants to win.") and there will be more of this to come. But having made this big, bold call, the Conservatives need to stick to it and resist the temptation to switch tack and revert to “banging on” about Europe immigration, not least since doing so will look panicked, desperate and insincere.