Guardian is hedging its bets:
"Leaders can survive challenges. In 1995 John Major was widely seen as doomed, but Michael Portillo postponed a decision to stand against him, Major easily saw off a challenge from John Redwood (the Catherine West of his day, in some respects), and Major survived another two years. In 2016 the vast majority of Labour MPs voted no confidence in Jeremy Corbyn, but he survived (because he was adored by Labour members, a benefit that Starmer does not enjoy). In 2006 Tony Blair accepted he would have to go. But he was allowed to work his notice for a year; Gordon Brown and his allies were powerful enough to force him out, but not to force him out quickly.
No one knows where this will end up. It could end up fatal for Starmer, but that is not a certainty."