This editorial will appear in tomorrow’s print edition.

So corporations and unions are short on opportunities to sway elections? Radio and television aren’t saturated enough with vicious hit jobs on the candidates they oppose?

Such is the logic of the U.S. Supreme Court, which shook decades of once-settled law Thursday by striking down crucial limits on corporate “campaign speech” – i.e., campaign spending.

The court’s five-member conservative majority overturned major precedents, a key provision of the McCain-Feingold campaign finance reform bill, and much of a 63-year-old law that barred companies and unions from raiding their general treasuries to mount media blitzes for or against specific candidates.

And just in time for this year’s congressional elections. Expect moneyed interests to play an even bigger role in the looming political battles than they had in the past.

The premise of the decision is that corporations and unions are the equivalent of individual citizens, and have nearly the same First Amendment rights as flesh-and-blood human beings. So the status quo – which allowed them to donate to regulated political action committees – was too restrictive.

The corporation-as-person idea is fundamental in the business world. But that’s an artifact of commercial law. The Constitution doesn’t demand that the principle be extended so broadly into the political arena.

The court’s decision does leave in place existing requirements that corporations disclose their campaign spending. Disclosure is the absolute of campaign finance law. In every election, citizens must be able to find out who is trying to influence their votes and factor that knowledge into their decisions.

But Tuesday’s ruling struck a de facto blow against disclosure by overturning the McCain-Feingold ban on corporate and union “issue ads” in the days immediately preceding an election.

Campaigns and PACs often pour truckloads of money into late hits – often exceptionally nasty and deceptive ones – the week before election day. When media attacks are launched at the eleventh hour, there’s often too little time for the public to find out who’s behind them, evaluate their motives and decide what to make of it.

So disclosure is effectively postponed until after the election. Now we face the prospect of big companies and unions employing this tactic to their hearts’ content.

Chief Justice John Roberts argued in his separate decision that the existing limits on corporate spending threatened “the vibrant political discourse that is at the foundation of our democracy.” Does Roberts watch television in election season? American democracy has its problems, but lack of “discourse” is not one of them.