Guaranteed minimum income

Just finished reading this interesting article from which I learned (among many other things) that both Richard Nixon and Martin Luther King, Jr. advocated for a guaranteed minimum income for all citizens regardless of work.

The wikipedia entry for the topic cited MLK:

In his final book Where Do We Go From Here: Chaos or Community? (1967) Martin Luther King Jr. wrote

“ I am now convinced that the simplest approach will prove to be the most effective — the solution to poverty is to abolish it directly by a now widely discussed measure: the guaranteed income.”

from the chapter entitled "Where We Are Going"

What happened to these discussions?