Charles Murray - conservative... came up with the original idea...
“Now Murray has come forward with a new book, In Our Hands: A Plan to Replace the Welfare State. He summarizes his proposal in this piece in the Wall Street Journal. “This much is certain: The welfare state as we know it cannot survive,” he begins. And so, “Instead of sending taxes to Washington, straining them through bureaucracies and converting what remains into a muddle of services, subsidies, in-kind support, and cash hedged with restrictions and exceptions, just collect the taxes, divide them up, and send the money back in cash grants to all American adults.” He comes up with a figure of $10,000 a year.”
http://www.usnews.com/opinion/blogs/barone/2006/03/29/charles-murray-abolish-the-welfare-state
The negative income tax (transfer payments, basically) shows up in Milton Friedman (not known to be a lib), and it was adopted and adapted by the 1972 McGovern campaign. It didn’t go well.