Rep. Chris Van Hollen (D-MD) has filed a lawsuit to force the Internal Revenue Service to block tax-exempt "social welfare" organizations from engaging in overt political activity, the New York Times reports.

Filed in U.S. Federal District Court for the District of Columbia and joined by campaign watchdog groups Democracy 21, Public Citizen, and the Campaign Legal Center, the suit argues that tax-exempt status under Section 501(c)(4) of the Internal Revenue Code should be granted to groups engaged exclusively in social welfare work and that the IRS should prohibit 501(c)(4)s from engaging in activity aimed at electing or defeating individual political candidates.

When determining whether a group is eligible for (c)(4) status, the government generally has said that the group's "primary" purpose should be social welfare, effectively allowing a significant amount of its work to be devoted to other activities, including partisan politics. Following the Supreme Court's deregulation of campaign finance laws in its Citizens United decision, 501(c)(4) groups, which are not required to publicly disclose the names of their donors, pumped $256 million into the 2012 presidential campaign cycle, triple the amount spent in the 2008 cycle.

Advocates of the lawsuit told the Times that the case law was clear: Congress never intended for (c)(4)s to be able to buy ads attacking a particular candidate. Moreover, they say, if Republicans in Congress really believe the IRS should not be trying to determine the appropriate balance between "social welfare" and political activity, they should be backing the suit. "If you agree the IRS should not be in the business of looking into the activity of every organization to determine how much is political versus social welfare, then you should welcome this," said Van Hollen.