The world, as Rob Colvile notes in his superb new book, The Great Acceleration, is getting faster. Alastair Campbell is said to have remarked that a politician cannot survive if they are in the headlines for more than nine days in a row – Maria Miller lasted just six before resigning over her expenses in April 2014. And now Naz Shah has resigned as parliamentary private secretary to John McDonnell just five hours after Guido Fawkes unearthed social media posts in which she argued that Israelis should be deported to the United States of America.

And as with Miller’s resignation, this was very much an occasion in which Shah had to be pushed onto her sword, rather than opting to fall into it herself. I’m told that she has no intention of standing down from the House of Commons select committee on home affairs, itself currently conducting an inquiry into Britain’s rising anti-Semitism problem.

The shadow Treasury team is itself, at least, somewhat insulated from further revelations about Shah’s social media activity, though unless or until Labour removes the whip it will continue to haunt the Opposition. But the swift turnaround is in stark contrast to the Labour leadership’s at times flat-footed response to anti-Semitism allegations, and, as with so many of the Labour party’s more effective moments, John McDonnell, the shadow chancellor, was heavily involved.

McDonnell has recognised for some time that being soft on anti-Semitism in the party could sabotage Labour’s chances in 2020. He believes, very firmly – perhaps more so even than Jeremy Corbyn – that the next election is eminently winnable for Labour and is one of the figures attempting to streamline the party’s platform, and focus on issues where the party is largely united, rather than have further rows over foreign policy and security. That's why he's been consistently more vocal in speaking against anti-Semitism than Corbyn, and has called for members found to be anti-Semitic to be banned for life.

I’ve written before that McDonnell – increasingly seen as the most effective Corbynite in the shadow cabinet – is talked of as a successor to Jeremy Corbyn. And his fans are not solely limited to the party’s left flank either, he has unlikely admirers among MPs from the centre-left, too.

Before appointing Shah he attempted to appoint a PPS from the party’s centre-left in an attempt to either a) build bridges with the leadership’s critics or b) bolster his own standing with MPs in the event of another leadership election (delete as applicable to your level of cynicism).

I’m told that the succession issue has receded somewhat as Corbyn himself is enjoying the job more than he has hitherto, after the government’s recent run of crises and a series of stronger performances at PMQs. McDonnell’s aides, meanwhile, insist that their boss has no designs on the top job. (It is, in effect, almost a dual leadership, similar to the Cameron-Osborne duopoly and the earliest years of Blair-Brown) But should that change, the outlines of the McDonnell offer to Corbyn’s critics in the party are becoming clear: that he offers a politics acceptable to the membership, done in a more professional way than at present.

At present, Corbyn's most virulent critics are mostly determined to "kill the politics as well as the man" in the words of one. But what you might call Corbynscepticism has a wide range of tones in the PLP, ranging from centre-left MPs who oppose him lock, stock and barrel, and MPs from the party's left who are concerned about Corbyn's operation and approach. If it becomes apparent that there is no way to enforce a change of political direction, the promise of the same politics at a faster pace may yet prove to be McDonnell's killer app as far that second group is concerned.