Comment by arrosenberg

The legislative process changed when the baby boomers entered Congress in the 1970s and started opening up committee processes and requiring publicly recorded votes. At the same time, there was a corporate reaction to a glut of environmental and consumer safety regulation. In 1973, you see the birth of the lobbying industry as ALEC is the first of many "think-tanks" to form.

Now legislators are accountable to corporate donors, not their constituents. It's easy to track which legislators provide a good ROI. There's more to it than that, but those are the major causal events that lead to the change in legislator incentives.