O'Rourke will not be the Democratic nominee; indeed, his advocacy for such a policy has ended his political career – at least in Texas.
And O'Rourke likely knows this – hence his advocacy for such a naïve and untenable policy; he’s falling on his sword in the service of a firearm regulatory measure what will never come to pass.
There might be a tiny minority of Democrats who support O'Rourke’s proposal – but the vast majority of Democrats want nothing to do with compelling Americans to ‘buy back’ their guns; it will guarantee a second Trump term.