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Picking up all the Green votes seems incredibly unlikely though, they're not a directly analogous party to Labour. The Green vote increased between 2017 and 2019 so they were clearly looking for something more than left leaning policies.
Plus, doing so without losing other support would be incredibly difficult. Trident is the obvious example: would binning that to win Green votes win more votes than the policy lost?
Yes. Labour loses seats by margins smaller than total Green vote share.