State of Washington sues Facebook and Google over failure to disclose spending

> If the problem is that money can buy unlimited federal power, then you can limit the federal powers available for purchase without curtailing the freedom of the citizenry to engage in political speech as they choose.

That's completely not a solution.

But if Jo Squillionaire wants people to have the freedom to contract their labor to a certain company indefinitely in the future, then Jo Squillionaire has the capacity to advertise enough to buy back that right. But I don't necessarily have the capacity to contradict him.

A more effective solution would simply be to limit a person's capacity to accrue wealth. If there's proper income and/or wealth taxes in place people can be rich enough without being too rich.

Money does, however, enable speech, and restrictions on things which enable us to exercise fundamental rights is at least potentially a restriction on that right. That's the framework the Supreme Court used.

If you disagree, consider: Pick a right you quite like (gun ownership, abortion, speech, voting in an election, etc.). Clearly a law banning that activity outright, or severely restricting it ("you can't obtain an abortion", "you can only speak in favour of Trump", "you can't own a handgun", "you can only vote for the Democratic candidate") would be absurdly illegal. It follows that a law preventing you from spending money on that right ("you cannot pay for an abortion", "you cannot spend money on criticising Trump", "you can't purchase a handgun", "you can't spend money travelling to the polls unless voting for a Democrat") would also be illegal (if severe enough at least).

The scope in which government can make your ability to exercise fundamental rights more difficult is non-zero, but sharply proscribed (witness the long string of court decisions striking down red state abortion laws).

It's possible that the restriction at stake in Citizens United was so minor that it should have been permissible, but I take your argument to be that it was anything but minor. In which case, the restriction probably was unconstitutional. In the US system, speech is protected, and (like it or not!) political speech is the most protected form. Any law which meaningfully impacts any real person's ability to speak about politics is presumptively unconstitutional, by design. And the more meaningful the restriction, the more that applies.

Limit on what? On speaking about politics? On buying ads? On paying people to write about politics? On hiring consultants to develop advertising strategies? On speaking about anything government cares about? So if NYT spends $1000 per subscriber on politicial writer's salaries in March, it has to be shut down until the next January because it's over the political speech limit?

This of course sounds insane, because you can't put limit on spending money on speech without putting limits on actual speech. Because it's one and the same - publishing speech costs money, and money is the way to get speech published.

Fortunately, US still has freedom of speech, which is not measured in dollar limits.

What is that strong support? We routinely see very well-moneyed campaigns lose. In the very last election in the US the losing candidate outspent the winning one - if you look at Super-PAC spending (which is the one considered most "dark and dangerous", right?) the losing campaign had gathered 3x from the winning one ($189.4M against $59.3M). Somehow turned out having money is not enough. So I'd like to see what you call "strong empirical support".