I’d like to think that, and I agree there’s an effect, but I’m pretty sure Burnham will win, and he’ll win by more than Reform + Restore. Burnham’s luck is that there’s no Green vote to speak of in Makerfield (whether of the eco-loon tendency or obsessive pro-Palestine voters). So his Labour vote is all about turnout, and I think he’ll get that sufficiently.
What I find surprising is not the support for Burnham in Makerfield but elsewhere in the party. He was nothing much in government and has shown no particular talent as mayor. As for likeability, he can’t be any less personable than Starmer but there’s nothing inspiring or widely appealing about him. Plus flip-floppery. And he’s a stale white man.
I still think Cooper would have been Labour’s best shot, but she’s (wisely) shown no ambition to be PM after Starmer.