This photo taken Oct. 3, 2014 shows the Supreme Court in Washington. (Susan Walsh/AP)

FIVE YEARS ago, the Supreme Court turned a corner on campaign finance. In Citizens United v. Federal Election Commission , the court held that corporations could undertake unrestricted independent spending in election campaigns, overturning decades of restrictions on corporate money in politics by saying that the money represented free speech . At the same time, the court, in a decision written by Justice Anthony M. Kennedy, emphasized the importance of disclosure of the sources of campaign money.

The court declared, “With the advent of the Internet, prompt disclosure of expenditures can provide shareholders and citizens with the information needed to hold corporations and elected officials accountable for their positions and supporters.” It also said that disclosure “permits citizens and shareholders to react to the speech of corporate entities in a proper way. This transparency enables the electorate to make informed decisions and give proper weight to different speakers and messages.” And the court expressed enthusiasm that technology today makes disclosure “rapid and informative.”

What went wrong? The court’s vision of disclosure and transparency is nowhere in sight. In fact, campaign finance in the United States has, by many measures, fallen into an era dominated by “dark money,” with donors hiding in the shadows and hundreds of millions of dollars of contributions flowing through politics without a trace of who gave it or why.

One factor in the rise of dark money is politicians such as Senate Majority Leader Mitch McConnell (R-Ky.), who became disclosure opponents once the court handed them a victory on unlimited contributions. The number of political groups that claim to qualify as tax-exempt social-welfare organizations and do not have to report their donors to the public has mushroomed. According to the Center for Responsive Politics, spending by organizations that do not disclose their donors has skyrocketed from less than $5.2 million in 2006 to more than $300 million in the 2012 election. The Internal Revenue Service should be deciding whether these groups legitimately qualify for tax-exempt status, but that’s made more difficult (intentionally) by Republican attacks and cuts to the IRS budget.

Meanwhile, the court’s endorsement of “independent” expenditures by corporations has led to a flood of money into campaigns from companies, unions and others. But far too many accounts have surfaced of collusion between supposedly independent groups and the candidates themselves to feel comfortable that all this campaign cash is truly independent.

The big-money dominance of politics has unsettled at least one conservative operative. The Post’s Matea Gold reported last week that tea party activist John Pudner is helping start a group devoted to reducing the impact of wealthy donors in politics. Mr. Pudner said he detected a growing public cynicism about politics: “People said, ‘Oh, you’re in politics — isn’t the whole deal now that people give a million dollars to politicians and get millions back?’ ”

Justice Kennedy was right about disclosure: It is the backbone of accountability. But the public’s ability to see who is contributing to politics has diminished since the justice wrote those words.