Ben Cohen wants to stamp your dollar.

That's because he doesn't think so much money - corporate money, in particular - should be spent on influencing U.S. elections.

The connection may seem tenuous, but bear with him. Cohen, the "Ben" of Ben & Jerry's ice cream, has organized a project called Stamp Stampede that encourages people to stamp anti-money-in-politics messages onto dollar bills, which will spread Cohen's political message as they circulate.

"Every time somebody stamps a bill, they're making a public statement that, 'I want money out of politics,'" Cohen told reporters on Tuesday, calling his project a "petition on steroids" and holding up a sign reading, "You Gotta Speak Out Against The Madness!" as he spoke.

To promote the campaign, Cohen hung around outside Union Station on Capitol Hill Tuesday afternoon, stamping people's dollar bills and giving them free ice cream. Passersby, intrigued by the Ben & Jerry's tent (where staff directed them toward Cohen, and the Stamp Stampede table, to acquire fake stamped dollars to "pay" for a free cone) stopped to hear Cohen talk about the problematic glut of political money that has followed the Supreme Court's Citizens United decision.

Smiling, he stamped their dollar bills with red-ink, rubber stamps reading "Stamp Money Out of Politics," "Not to Be Used for Bribing Politicians," "Corporations Are Not People," "Money Is Not Speech" and "The System Isn't Broken, It's Fixed."

"Only those people who have a lot of money are heard," Cohen told ABC News. "The politicians do whatever the people who give them the money say that they want in order to get the money, 'cause they want the money."

Cohen estimates he's disseminated 8,000 stamps - he sells them through the Stamp Stampede website - and his group claims that each stamped bill reaches 875 people.

As a light drizzle began outside Union Station, a congressman, Rep. Rick Nolan, D-Minn., came up to congratulate Cohen, who enthusiastically shook his hand. The customers waited in the rain, smiling as Cohen slammed the red stamps down on their dollars. Young men dressed in cow suits made small talk at the end of the table.

Cohen said he'll hold more of these rallies in the future, and he insisted the whole thing is legal, despite a U.S. law against defacing currency.

"You know, a lot of people think that, but it's not," Cohen said. "We've been through the law, we have lawyers that have been through the law, we have a legal opinion on our website. When you get into it and you read the law, it's clear that they anticipated that people were gonna be marking money or writing money, and they'd even gone so far as to say that these are specific things you cannot do."

Stamping bills to protest election spending, evidently, isn't one of them.

The whole effort is aimed at passing a constitutional amendment stating that "corporations are not people" and "money is not free speech."

Cohen said such an amendment would invalidate the Citizens United decision that gave rise to super PACs. To do that, Cohen will need approval from legislatures of constitutional conventions in three fourths (38) of the 50 states.

Little did Cohen know, as he convened his "stampede" and ice cream social at Union Station, half a mile away in the U.S. Capitol, Sen. Jon Tester, D-Mont., was holding a news conference to unveil just such a constitutional amendment, stating that corporations are not people. Sen. Tom Udall, D-N.M., rolled out his own, stating that the federal government can regulate political fundraising and spending on federal elections.

All three face nearly impossible odds. Cohen said a constitution amendment is possible.

"I do think it could happen," Cohen said. "Sure, amending the Constitution is a really hard thing to do, but it's been done before, and the times when it's been done is when there's been overwhelming public support, and that's what there is."

Whether or not he succeeds, there will be free ice cream along the way.