Editorial: Campaign-finance Future Haunted by Montana's Past

Montana's law stood for a century as governors and legislators of both parties backed it. Today, according to the state attorney general, the average winning Montana state senate candidate spends an almost trivial $17,000. Campaigns consist mostly of making speeches and visiting door to door, not slick, expensive TV commercials. The state's top court upheld its law on the grounds that any reasonable reading of Montana's history would conclude that massive flows of money into politics are corrupting.

But on Monday, a 5-4 majority on the U.S. Supreme Court struck down Montana's law on the grounds that it conflicted with its ruling in Citizens United v. the Federal Elections Commission. That 2010 decision allows companies, labor unions and wealthy individuals to spend unlimited sums to advance causes and candidates. The justices said then that they did not think unlimited political expenditures would give rise to corruption, or even the appearance of it.

Perhaps the majority has not been paying attention. Already this year, several congressional primaries have been won by candidates who benefited from a flood of last-minute money into independent advertising. In some cases, voters didn't know the identity of the people giving this money or the donors' agendas...