Tax-exempt nonprofit organizations supposedly devoted to social welfare" can spend large amounts of money to influence elections without publicly disclosing the identities of their donors. But instead of cracking down on the use of "dark money" for political purposes, the Internal Revenue Service has decided to stop requiring these groups to reveal even to the government the sources of their funding. On Monday, the IRS and the Treasury Department announced they would no longer require 501(c)(4) groups ... to supply the government with the identities of donors who gave more than $5,000 in a single year. It's a step backward that could make it easier for money from foreign sources to find its way into U.S. elections. But while this week's policy change may not affect what the public may learn about political spending by so-called social welfare groups, it could make it more difficult for the government to police laws against spending by foreigners on U.S. elections. Fred Wertheimer, president of the campaign reform group Democracy 21, warned that, with the end of the reporting requirement, "there is no way to determine if a 501(c)(4) advocacy group that is spending money to influence federal elections is taking that money from [a] foreign interest."