Seems like an idea case for letting the “states as laboratories of democracy” sort it out. If some states legalize, and it doesn’t go well, then it will be to the benefit of those states that don’t.
I support the idea that the States should be allowed to “experiment”. The problem is that with leftists, no amount of bad outcomes will persuade them to reverse course on a policy. Look at welfare. It’s damned hard to push the camel away when he’s got his nose under the tent.