A couple of days ago, I saw TV footage of the outspoken Labour MP Jess Phillips on the campaign trail, seeking re-election in her suburban Birmingham constituency.
She was asked which issues voters mentioned most often on the doorstep. Ms Phillips did not miss a beat.
‘Immigration comes up…’ she said thoughtfully. And then, as if remembering herself, she started talking about bin collections instead.
It was, I thought, an enormously revealing moment. For there is no issue so potentially dangerous as immigration. Many people have intense feelings about it, and many feel unable to raise them publicly.
Even in private, self-consciously tolerant people discuss immigration very tentatively, if at all.