More or less - if the polling wasn't what it was, if they didn't think the local elections were a harbinger of a national contest, Starmer would probably ALREADY be out. And if you're going to use him as a human shield to get your ducks in a row long enough to install Andy Burnham - it doesn't really do you a lot of good to undercut your own Prime Minister in the meantime.
But I am being told the decision has been made. It's a done deal. There is no bridge back for Keir now.