The Supreme Court’s Citizens United decision that triggered an avalanche of corporate political spending also contained a proposal for greater public disclosure from corporations that would prefer to write their checks in the shadows.

Transparency, the court advised, would let voters decide for themselves “whether elected officials are ‘in the pocket’ of so-called moneyed interests.”

Since that 2010 decision, corporate and Republican opposition has snuffed out congressional attempts to require donor transparency and accountability.

All the more compelling, then, that the Securities and Exchange Commission, following an impressive petition campaign, is considering a regulation mandating that publicly traded corporations disclose all their political donations to their shareholders.

Corporate donations are not the full sum of the dark money universe, but forcing publicly traded corporations into the sunlight would be an enormous step toward facing the threat of political corruption posed by stealth donations.

The petition drive, underway for more than a year, has prompted close to 500,000 comments, a vast majority favoring disclosure. A disclosure regulation could be proposed by the SEC officials in a matter of weeks.

The fury of the opposition is already evident as trade associations like the U.S. Chamber of Commerce issue alerts to members that free-speech rights are about to be trampled. Not according to Justice Anthony Kennedy in Citizens United, who noted that “shareholder objections raised through the procedures of corporate democracy” would provide accountability by companies now free to hide donations through trade associations.

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Mary Jo White, the new SEC chairwoman, has promised dynamic changes in corporate oversight. The looming disclosure fight provides a test.