The great gulf between left and right yawns deeper and wider. One way or another, the Gorton and Denton byelection this week will reveal this profound tribal divide. Those in the progressive bloc – Labour, Lib Dem, Green, SNP, Plaid – are very different kinds of people to the blues, with diametrically opposed attitudes. In more centrist days there was some shifting across the red/blue line as both main parties stole some votes from each other. That’s over. Everyone now is in one or the other trench (or a non-voter), though many are undecided which party to back within their bloc. Ever since what psephologists call the “Brexit realignment”, the split has become unbridgeable.

Labour has been getting this near-catastrophically wrong in the past 18 months, pursuing voters who will never support the party, while at the same time chasing away its own supporters. The architect of this blunder, Morgan McSweeney, is gone, though the leader is responsible for where his party is led – or misled. No more of that hippy-punching strategy that avoided anything sounding too leftwing. It was designed to attract the right but, of course, it didn’t.

The chasm dividing the two tribes is revealed in Britain’s Party Members research by Prof Tim Bale, Prof Paul Webb and Dr Stavroula Chrona. Reform voters are no closer to Labour on economic than on social and migration issues. They are planets apart on everything and Labour needs to see it. A majority of Reform members and voters want to cut tax and cut public spending, while the progressive bloc overwhelmingly chooses the opposite. On the climate crisis, 86% of Reform supporters........

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