Photo by James Manning/ PA via Alamy Keir Starmer will try to save his political career this morning by giving a speech in which  he will admit mistakes and say “incremental change won’t cut it”.  The most immediate consequence of the speech will be whether it makes Catherine West – the backbencher threatening to launch a leadership challenge this morning – think twice. West has said she might step down her plot if Starmer shows sufficient rhetorical fire in his belly. But that will be quite a difficult metric for outside observers to judge – and so we will have to wait and see how West responds to the speech. As she told me in an interview at the weekend, her decision to challenge Starmer was done on the fly – she had not read the party rules on launching a contest before announcing) and motivated by a visceral reaction to the results in which one of her best friends  lost their safe Labour council seat in North London.…