Bernie Sanders, answer why your presidential campaign even needs a dark money group Common Cause has filed a formal complaint against Our Revolution with the FEC. It is not easy for a Democratic candidate to get on the wrong side of Common Cause: Our view

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Ten years ago, when the Supreme Court struck down a bipartisan campaign finance law and opened up the spigots for political giving, experts predicted what this would mean. Corporations would become important brokers by using their new powers to spread money around. And Republicans would be the big beneficiaries.

In reality, the biggest legacy of the Citizens United ruling has been so-called dark money — money raised by independent groups from unknown donors spent on behalf of a candidate, multiple candidates, a party or cause.

And the biggest user of this dark money — at least until this fall when President Donald Trump is expected to release a torrent of it — has been Democrats. In the 2018 midterm elections, dark money groups spent about $150 million. Liberal groups accounted for 54% of that, and much of it from a single organization called Majority Forward.

Sanders founded Our Revolution

This year brings a new chapter in the story. Sen. Bernie Sanders, I-Vt., has created, and is the beneficiary of, a new kind of dark money group called Our Revolution.

OUR REVOLUTION: Our mission is much more than electing Bernie Sanders

What makes Our Revolution different is that it is designed to advance Sanders’ cause against other Democrats in the primaries, rather than against a Republican in a general election. It’s one thing to say you have to play the dark money game because the other side surely will. It is quite another to be first off the mark in bringing its corrosive powers into a new area.

Sanders has long been a big critic of money in politics, often criticizing political action committees and the candidates who benefit from them. To then go out and found a group like Our Revolution is hypocritical.

Before and after Iowa caucuses

Our Revolution claims to voluntarily report all donors who give more than $250. But it doesn't file documents with any agency, provide identifying information about individuals or specify how much they gave.

Our Revolution has set off a kind of arms race. With Sanders' poll numbers rising ahead of Monday's Iowa caucuses, a dark money group funded to support Israel has come out against him. Some moderate interests in the Democratic Party are considering creating anti-Sanders groups should he do well in the early contest for the party's presidential nomination.

Last month, Common Cause — a watchdog group that fights against gerrymandering, voter suppression and the role of money in politics — filed a formal complaint against Sanders and Our Revolution with the Federal Election Commission. It is not easy for a Democrat to get on the wrong side of Common Cause.

Our Revolution has been central to Sanders’ street-level organizing. And it has selectively gotten involved in his spats with other Democrats. Late last year, Our Revolution activists showed up in Pete Buttigieg’s home base of South Bend, Indiana, to highlight the former mayor’s opposition to mandatory "Medicare for All" and other issues.

At the very least, Our Revolution needs to reveal all its donors, along with where they live and and how much they give.

Beyond that, Sanders has to answer why he even needs such a group. He has had little problem raising money in the open, the old-fashioned way.

The Citizens United case has produced a decade-long string of unintended consequences. It would be highly ironic if one of them is progressivism abandoning its soul in the name of political expedience.

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