Unlike candidates for the White House and the House of Representatives, U.S. Senate candidates don’t electronically file their campaign finance disclosures. They send them through snail mail instead, and that means that every election millions of dollars in special interest money remains hidden from the public until after the votes have been tallied.

Way back in 1999, members of the Senate carved out a special loophole that allowed them to ignore the Federal Election Commission’s (FEC) regulations on electronic filing. The FEC’s e-file process requires candidates to directly upload their reports so they can be published quickly online (within 24 hours as mandated by law) in an accessible format that allows for journalists and citizens to quickly analyze a candidate's donors. That’s how House and presidential candidates have been doing it since 2001, but because of a technicality in the way the law was written, Senators and Senate candidates are exempt from the e-file process.

It’s 2015, and this is how US Senators file their disclosures:

Step 1: Senators print their campaign finance disclosures on paper and mail them to the office of the Secretary of the Senate.

Step 2: The Secretary of the Senate then scans the printouts and emails them to the FEC as digital image files.

Step 3: The FEC prints them out and then sends the paperwork to a private contractor.

Step 4: The private contractor keys all of the information into a computer program and sends a data file back to the FEC.

Step 5: The FEC then posts the information on the Internet.

The net result? Public disclosure of campaign contributions are delayed by weeks or months, and as much as $500,000 in taxpayer money is wasted on the process each election cycle.

While this system is a bad deal for the public, there is a clear benefit for the campaigns. Candidates typically raise more money as election day approaches, and the paper filing system's slowness means that Senate candidates’ final, pre-election filings are often not made public until after election day. That creates a window for candidates to accept donations from controversial donors—say, scandalous organizations or public figures—without risk of being held accountable by voters.  

To their credit, about one-fifth of senators have begun voluntarily filing their disclosures electronically, and 32 are co-sponsoring legislation that would require all senators to e-file. But bills to mandate e-filing by senators have been introduced repeatedly over the years only to die through anonymous holds, filibusters, or poison-pill amendments. The current leader of the Senate, Sen. Mitch McConnell (R-Ky.), has been one of the top opponents of the legislation for years.