I don't think it's so much goal post moving as a lot of us never claimed it buys elections. My assertion has always been that generally speaking if you want to be competitive politically you need to scratch the backs of elites to get the proper funding to be relevant in elections. It's not an absolute, rather that there is excessive corporate influence that undermines the political process
I'm pretty sure everyone who wants campaign finance reform claims that money buys elections, unless a situation doesn't fit that narrative in which case the goal posts are shifted or moved. I'll check out your links though, thanks very much for those.