For Starmer, the best way to take Johnson down right now may be to agree with him | Rafael Behr

Voting with the government on plan B is not just in the national interest - it will aggravate splits in Conservative ranks

Leaders come and go, policies move with the times, but the challenge facing Labour is unchanged for generations: to win an election it must appeal to Conservative voters, which does not come easily to a party that struggles to imagine why anyone in their right mind would be a Tory.

Boris Johnson makes that empathic leap trickier still. Those who are unmoved by the magnetism of his character find it more alienating than any disagreement over policy or ideology.

Rafael Behr is a Guardian columnist