Lately, U.S. Senate Majority Leader Harry Reid has been denouncing David and Charles Koch, calling the oil billionaires "un-American" as they funnel tens of millions of dollars into campaigns to defeat Senate Democrats.

There's plenty to criticize. The Koch brothers are notorious for cloaking their campaign money behind a web of tax-exempt social welfare organizations. But Reid has an issue of secrecy in his own house, one he ought to remedy.

Unlike candidates for most city councils, state legislatures, the U.S. House of Representatives, and president of the United States, U.S. senators refuse to file their campaign finance reports online.

The reason is simple. Senators make their own rules. Some of them don't want to make it easy for the public to see who funds their campaigns, or how they spend their campaign money.

In 2007, Sen. Dianne Feinstein, D-Calif., promised to fight to require online filing. She failed. In 2014, roughly 80 senators, plus most Senate candidates, use snail mail or couriers to deliver their paper reports to an obscure Senate office a few blocks from the Capitol, far from voters' inquiring eyes.

Sen. Barbara Boxer of California is one of 20 senators who voluntarily filed their year-end 2013 campaign finance reports online with the Federal Election Commission earlier this year.

Some of the 20 filed for the first time, joining Boxer and a smattering of others who long have made it a routine practice. Voluntary filing is an iffy proposition. Some senators who make online filings do so late, or skip online reporting altogether. Feinstein, for example, usually files electronically, but didn't send her year-end 2013 report this year. Laxity is understandable. The FEC cannot fine them for failing to adhere to deadlines, since online filing is not required.

FEC records show that among senators who fail to voluntarily file their reports online are Reid, Dick Durbin, D-Ill., and Senate Republican leader Mitch McConnell, plus potential 2016 Republican presidential candidates Rand Paul of Kentucky, Ted Cruz of Texas and Marco Rubio of Florida.

The FEC obtains the paper reports, copies them, and delivers them to a company in Virginia, where keypunchers type donor information into computers. Once the keypunching is complete — days or weeks later — the FEC puts the reports online.

The commission estimates the laborious process costs taxpayers $430,000 a year, unnecessarily, all because the Senate is cavalier in its treatment of the public's right to know who funds their campaigns.

The Sacramento Bee's editorial board has written about this insult to the citizenry before. The Senate's hesitancy to step onto the World Wide Web is worth pointing out again, as The Bee and several other McClatchy newspapers are doing, in recognition of Sunshine Week, a project led by the American Society of News Editors that is intended to underscore the importance of open government.

Senators fail to file their reports online because they understand the power of disclosure. They know that any voter with a computer could pick through their reports and see that they take money from, say, tobacco- or oil company-funded political action committees, or that the bulk of their money comes from various interest groups in Washington.

The nonprofit Center for Responsive Politics, which tracks federal campaign money, is petitioning Reid to bring to a vote legislation by Sen. Jon Tester, D-Mont, which would force senators to file their reports online.

The bill has 37 co-sponsors, including 29 Democrats, six Republicans and two independents, although, ironically, a majority of the 37 fail to file their reports online.

"When will you bring the Campaign Disclosure Parity Act to a vote?" the petition directed at Reid asks.

It's an excellent question.

Political prognosticators believe Republicans could take control of the Senate in the 2014 elections, in part because of the tens of millions that the Koch brothers will spend.

Reid believes that attacking the Kochs is good politics as he defends his fellow Democrats. Perhaps he is right. But he'd have greater moral authority if he proved his commitment to openness by forcing a vote on legislation requiring senators to finally enter the Internet age.

This editorial orginally was published in the Sacramento Bee.