They're from the American Legislative Exchange Council, which essentially is a group bringing together conservative legislators and corporations who want changes in the law, with those corporations actually helping write model legislation that is taken back to individual states. ALEC is basically a giant corporate advocacy/lobbying group in the guise of an "educational" "charity" -- and its members include both corporations and thousands of conservative state legislators.
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=439x591230Check the replies in that topic, not just the OP. Most people have no idea how influential ALEC is and how many of these bills are copying ALEC's model legislation.
The Arizona immigration law came out of an ALEC task force whose members include the Corrections Corporation of America (CCA), which profits from such bills.
The union-busting measures in Walker's budget copy ALEC's model legislation for "budget reform" -- which also includes privatization, which is being pushed too (power plants in Wisconsin, prisons in Ohio, etc.).
The bills designed to nullify federal health care reform come from ALEC.
Ditto various bills designed to roll back environmental regulations.
Milbank SHOULD be aware of just which bills come from ALEC and which are most likely isolated Tea Party craziness (the GA plan to abolish driver's licenses, for instance -- you know insurance companies won't support that and ALEC is nothing if not pro-business). But as far as I've been able to discover, Milbank has never written anything about ALEC.
The Tea Party is an astroturf front useful for political campaigns. But the key player in this legislative blitz we're seeing is ALEC.
The Koch brothers provide part of the funding for both. But ALEC brings together much more corporate influence on legislation. This isn't just about the Koch brothers.