In March 2002, the Bipartisan Campaign Reform Act -- commonly known as McCain-Feingold for its two lead Senate sponsors -- became law. It sought to make political donations far more transparent and to keep unregulated "soft" money out of the political process. A decade removed from the law's passage -- and in the wake of the landmark Citizens United Supreme Court ruling in 2010 -- vastly more untraceable money is flowing through the system than ever before.

According to tabulations made by the indispensable Center for Responsive Politics, there has been more than $50 million in "dark money" -- cash whose source need not be disclosed -- has already been spent on House and Senate contests, a massive increase from even the 2010 midterms when, at this point in the election cycle, just $6.6 million in dark money had been spent.

The chart below -- put together by CRP  -- is eye-popping.

Image courtesy of Center for Responsive Politics

What's even more remarkable is that if history is any guide, we ain't seen nothing yet.

By the end of the 2010 midterms, more than $130 million had been spent on elections by groups that don't disclose their donors.  So, if $6.6 million: $130 million then $50 million: ????.  "If the rate of spending from previous cycles continues, the totals could reach upwards of $730 million or — if the rate seen in the last midterm holds — edge close to $1 billion," writes CRP's Robert Maguire.

That's "billion" with a "b".  In a midterm election in which no one thinks the House is in play. Imagine what 2016 -- with a contested presidential race as well as battles for the Senate and House majorities -- will be like.