Keir Starmer had no option but to say - as he has just done - that he would resign if fined for breaching Covid rules, as I already pointed out on Friday when Durham Police announced it was investigating whether his beer and curry last April was work sustenance or an illegal party.
There were two reasons why he had to put his job on the line.
First, he would never get over the charge of grotesque hypocrisy had he failed to do this, given that he and his party have repeatedly and urgently called on Boris Johnson and Rishi Sunak to quit, after they received fixed penalty notices for attending the PM’s birthday party.
Second, and this is short-term politics, tomorrow Starmer would not have been heard in the important Queen’s Speech debate on Johnson’s new legislative programme, because Tory MPs would have repeatedly interrupted his address to taunt him about the police probe.
To be clear, the idea that ministers or party leaders should not break the criminal law and remain in office is not a revolutionary one. It is implicit in the ministerial code of conduct that every PM - including the current one - authorises and pledges to follow.
But even if the PM is fined a second or third time, his close colleagues do not expect him to quit. “Boris told me ‘you’ll need a flame thrower to get me out’” said one.
So if Starmer has retaken the moral high ground, it’s to embarrass Tory MPs who are not pressing a vote of no confidence on the PM rather than an attempt to embarrass a PM who is not famous for feeling shame.
Starmer has created some deadline pressure for the PM however. It would be far, far better for Boris Johnson if all the Metropolitan Police investigations into Downing Street parties were done and dusted pronto - even if the PM is fined again - so that the report by Cabinet Office official Sue Gray into them can be published before Durham Police reach their verdict on Starmer.
Because until Starmer is either fined and resigns or is cleared, any charge the Labour leader lays against Johnson is less stinging.
But if the Met Police and Gray verdicts against Johnson come after Durham decides, and if those verdicts reinforce and multiply the existing guilty verdict against Johnson, then the big politics would be terrible for the Tories.
Because at that juncture either Starmer will have been proved innocent or he will have resigned. And every Tory MP would have the challenge of explaining to voters why the same rule didn’t apply to Johnson.
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