As secret political spending escalates in the final weeks before Election Day, it’s not too early to ask: What can be done to bring “dark money” out from the shadows?

Even more than super PACs, secret money may well define the post-Citizens United era. As of Oct. 1, political spending by outside groups that do not disclose their donors had hit $122.7 million, according to the Center for Responsive Politics – more than twice their totals at the same point in 2010 and 2008, which hovered in the $45 million to $47 million range.

The rub for secret money critics is that pulling back the curtain on such groups is harder than it looks. The DISCLOSE Act, the campaign finance transparency bill authored by Democrats on Capitol Hill, faces unanimous GOP opposition. The Federal Election Commission is hamstrung by partisan gridlock; the IRS by its aversion to political controversy.

Still, there are several modest, practical steps that Congress could take to bring undisclosed campaign money into the open, and some even have bipartisan support. Many simple, interim fixes focus on the IRS, an agency that has largely been left out of the campaign finance debate but whose importance is growing as political money travels further underground.

Historically, the IRS has protected the anonymity of donors to 501(c)(4) social welfare groups, along with other tax-exempt organizations such as 501(c)(3) charities and 501(c)(6) trade groups, and for good reason. As the Supreme Court established in its landmark 1958 NAACP v. Alabama ruling, anonymity protects potentially unpopular citizen groups from government intrusion.

But this election’s secret money is being spent not by vulnerable civic groups, but by multimillion-dollar campaign-style
organizations. The big spenders are
501(c)(4) tax-exempt groups whose organizers say they’re promoting the social welfare but whose hard-hitting ads, robocalls, direct mail and door knocking operations give them all the trappings of political campaigns. Tax law expert Frances Hill, of the University of Miami, has dubbed these players “super (c)(4)s.”

The top two such groups – the GOP-friendly nonprofits Crossroads GPS and Americans for Prosperity – had collectively spent $173.8 million on ads targeting candidates as of late September, according to the Sunlight Foundation. That’s more than the top four super PACs combined, which, according to Political MoneyLine, have doled out $170.2 million.

“Wealthy, powerful individuals and financial interests are not the equivalent of a small, vulnerable, persecuted minority,” noted Trevor Potter, president and legal counsel of the nonpartisan Campaign Legal Center and a former FEC chairman.

An obvious first step for the IRS, Potter and other campaign finance experts say, would be to draw a clear, bright line between legitimate “social welfare” spending and overt campaign spending. IRS regulations now rely instead on a complex, multipart test based on “facts and circumstances” to draw that line, leaving political players on both sides of the aisle wondering just what’s permitted.

“The IRS standards for what constitutes political intervention is an 11-part test, which is thoroughly subjective,” Potter said. “I think it would be very helpful from an IRS standpoint and a tax-exempt-law standpoint for the IRS to clarify what 501(c)(4) organizations can and can’t do.”

Other relatively straightforward fixes that tax experts say Congress could ask the IRS to pursue include:

. Imposing new disclosure rules on noncharitable tax-exempt groups that are funded by a limited number of people. Ellen Aprill, a tax law professor at Loyola Law School in Los Angeles, argues that this would insulate broad-based social welfare groups from unwanted scrutiny but would shed more light on groups that rely on a few big donors. Aprill also favors taxing political activity by noncharitable tax-exempt groups.

. Require tax-exempt groups to disclose contributions and expenditures larger than $25,000, an idea favored by Donald B. Tobin, a law professor at Ohio State University’s Moritz College of Law. (Like Aprill, Tobin would exempt charities.) Tobin also suggests allowing for external complaints regarding abuses of tax-exempt status and putting enforcement in the hands of an independent, nonpartisan commission made up of former IRS veterans.

. Create a joint enforcement mechanism between the FEC and the IRS, whose regulations do not match up so that political players fall between the cracks. Such interagency cooperation has plenty of precedents, argues Hill.  

Such ideas are not as dramatic as passing a Constitutional amendment to reverse Citizens United v. FEC, the 2010 Supreme Court ruling that opened the way for unlimited and undisclosed political spending. Nor are they as popular with watchdogs as matching low-dollar contributions with public funds, an idea that has generated renewed interest among reform advocates.

But while more-sweeping reforms may gain traction over the long haul, their short-term prospects are dim. Amending the Constitution is a quixotic quest at best. Public financing will be dismissed by Republicans out of hand as “taxpayer-funded” campaigns.

In the meantime, secret money is compounding public alarm over Citizens United. It’s alarming enough to many voters that billionaire CEOs appear to be bankrolling politicians. Even worse is the prospect that most of these large contributions may never see the light of day. All the more reason for Congress to consider every avenue, small and large, on the hard road to transparency.