The Obama administration is pushing for stricter limits on the use of tax-exempt organizations for political campaigning. The new rules proposed Tuesday have to do with groups organized under Section 501(c)4 of the tax code. The groups have been viewed by many as the biggest abusers of modern campaign-finance rules and were at the center of the IRS scandal.

It turns out that the origins of section 501(c)(4), providing exemptions for “social welfare” groups, are surprisingly foggy.

“There’s almost no history on it,” said New Mexico tax attorney Robert J. Desiderio, a former dean of the University of New Mexico School of Law, in an earlier interview with Law Blog....

The roots trace back a century ago to when Congress enacted the Revenue Act of 1913, also known as the “Underwood Tariff Act,” according to Mr. Desiderio and other tax scholars....