Activists opposed to secret money in politics have stepped up a pressure campaign aimed at the Securities and Exchange Commission, targeting two major Washington, D.C., Metro stops with billboards and street demonstrators urging the SEC to adopt a new corporate disclosure rule.

Demonstrators will be converging on the Union Station and Tenleytown-AU Metro stations at rush hour starting this week to hand out “trading cards” featuring the five SEC commissioners. They will also be sporting sandwich boards calling on the agency to take action. A trio of bold, red and yellow billboards in each of the stations includes the message: “With Just 3 Votes, the SEC Can End Secret Corporate Spending in Our Elections.”

Organized by the Coalition for Accountability in Political Spending, which represents public officials bent on curbing corporate election activity, the actions are part of an ongoing campaign to push the SEC to adopt a disclosure rule that would require publicly traded corporations to report all direct and indirect political spending to the SEC in public filings.

A group of 10 corporate and securities law experts first petitioned the SEC last August to adopt the rule, which would disclose the money corporations give to politically active trade associations and nonprofit advocacy groups, and that now flies under the radar. A strange-bedfellows Corporate Reform Coalition, spearheaded by Public Citizen, has generated a record 292,000 public comments to the SEC on the issue.

“This is becoming much more than a cause for insiders,” said New York City Public Advocate and CAPS founder Bill de Blasio. “We’re going to pull in grass-roots shareholders, pensioners and voters — all of whom have a stake in the SEC taking action.”

The choice of the Tenleytown-AU station as a location for billboards and street action was no accident: That’s the stop that SEC Chairwoman Mary Schapiro uses for her commute, said Lisa Gilbert, acting director of Public Citizen’s Congress Watch.

CAPS and other coalition members have set out to pressure the SEC to at least put the disclosure rule on the commission’s next semiannual regulatory agenda this winter, and to boost their public comments to the SEC to 500,000.

“They have the power to disclose political spending, and they have been sitting on the solution,” Gilbert said of the commissioners.

SEC Commissioner Luis Aguilar announced his support of the disclosure rule in February. Sen. Bob Menendez (D-N.J.) has written to the SEC, along with several fellow Democrats, to urge commissioners to adopt the rule. Menendez has also authored legislation that would give shareholders the power to vote on corporate political expenditures.