What would it take to overturn Citizens United?

I hope this type of question is allowed on this sub- I’m asking lawyers because it was a legal case at the US Supreme Court that allowed for an explosion of dark money into politics based on the rationale that money is speech. The case invalidated a bipartisan law on campaign finance reform. Would another federal law be able to restore the core parts of it, or is the only solution a constitutional amendment? I guess the third option would be a similar case at the court with a progressive majority, but that’s seemingly a much longer term prospect.