John McCain's warning about dark money is real. Stop campaign finance corruption. Many Republicans and Democrats on Capitol Hill are taking bold, important steps to fight dark money. We must arm ourselves against outside influence.

Tim Roemer and Zach Wamp | USA TODAY

According to Sen. John McCain, R-Ariz., a secretive, corrupting campaign finance system is at the root of political dysfunction dividing Americans across the country — and he says Congress better fix it.

He candidly writes in his forthcoming memoir, The Restless Wave, that non-profit social welfare organizations — the 501(c)(4)s that hide their donors and fight to keep them secret — “are often financed by one or two of several billionaires” who yield enormous influence.

Just last month, we learned a dark money group spearheaded a $100,000 ad campaign against Senator Rand Paul, R-Ky., accusing him of representing the interests of terrorists over his Kentucky constituents. The ad was in response to his opposition to Gina Haspel as the nominee to head the CIA — during a cycle when Paul is not even up for re-election.

We know next to nothing about the group, but according to reporters it is tied directly to other organizations that are part of a “scheme to launder dark money” into congressional and presidential contests. It is notable that the group attacked the junior senator from the same state as Senate Majority Leader Mitch McConnell, R-Ky., who remains firm in his resistance to providing transparency in the political system.

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The concept of dark money is still a relatively new phenomenon as far as elections go. The spending of millions of dollars by anonymous outside groups has really only become an issue since the Supreme Court’s 2010 Citizens United decision and has come to infect and contaminate every facet of politics in America, from state races, to congressional contests and even President Trump’s inaugural committee.

A wealth of facts underscores that McCain is right on both counts: So-called dark money organizations continue to spend tens of millions of dollars attacking legislators from both parties as members of Congress continue to sit on their hands, incapable of finding a bipartisan solution. Opaque organizations fueled by shady donors are wickedly attacking members of Congress and they are doing nothing. Meanwhile, the last major campaign finance overhaul in this country, the Bipartisan Campaign Reform Act of 2002, is more than 15 years old.

It’s perfectly appropriate that its nickname (McCain-Feingold) includes McCain, whose politics are grounded in a time when members of Congress were willing to collaborate in doing what was right, spending political capital to actually pass legislation. McCain also writes that, “Principled compromises aren’t unicorns. They can be found when we put political advantage slightly second to the problem we’re trying to solve.”

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Moreover, looking into our crystal ball, we will take the senator’s comments one step further and point out that, according to intelligence reports, in 2018 we are likely to continue to face something even more diabolical: Foreign disinformation campaigns from anonymously funded governments, inflicting attacks on American national security. Congress has refused to hold a hearing on potential legislative solutions, like the bipartisan, bicameral Honest Ads Act. Our 20th century laws are greatly overmatched by the 21st century reality of zombie armies, bot farms, cyber weapons and foreign governments.

Whether it is emanating from one or two donors inside the U.S. or one or two foreign countries, these immoral and personal political attacks, and nefarious cyber intrusions, are breeding distrust among Americans about our political system. These covert political maneuvers do not reflect our Founders’ promise about America and the system of government we have worked to improve over time. As Supreme Court Justice Antonin Scalia wrote in a 2010 case: "For my part, I do not look forward to a society which, thanks to the Supreme Court, campaigns (are) ... hidden from public scrutiny and protected from the accountability of criticism. This does not resemble the Home of the Brave."

Congress must do its constitutional duty and protect our country. Many Republicans and Democrats on Capitol Hill are taking bold, important steps. More than a dozen members on both sides of the aisle joined the bipartisan Congressional Reformers Caucus, who seek to address the influence of money in politics and dysfunction on Capitol Hill. Additionally, legislation to overhaul the Federal Election Commission has growing bipartisan support. The Honest Ads Act is gaining momentum too.

Yet the longer we allow deep-pocketed donors to tilt the electoral playing field, and take little action against hostile foreign powers attacking our political discourse, the more tribal division you will see in our United States.

Democrat Tim Roemer is a former U.S. ambassador to India and a former congressman from Indiana. Republican Zach Wamp is a former congressman from Tennessee. Follow them on Twitter: @Tim_Roemer and @zachwamp