This is actually a good thing for Labour, I think. Although not for, e.g., Labour councillors in cities in the short term.

It’s a challenge that plenty in Labour are taking seriously. “Polanski is a real threat,” says a senior source, warning that the old assumption that “these people have nowhere else to go” no longer holds. No 10 has long believed that the Greens […] pose the biggest threat (a prediction that has so far been borne out).

If ‘senior source’ here is actually being listened to, that’s all to the good.