One critic called the proposal, which describes green investment policies as a form of "energy discrimination," a "desperate attempt by fossil fuel companies and their lobbyists to maintain their profits."

"Death is an escape hatch for David Koch while the rest of us are left scrambling for the emergency brake before we go over the cliff."

"A majority say yes to healthcare for all! The benefits: Guaranteed medical care, dental, vision and hearing, for all Americans, free at the point-of-care. The savings: $2 trillion over 10 years."

"If every major country on Earth can guarantee healthcare to all, and achieve better health outcomes, while spending substantially less per capita than we do, it is absurd for anyone to suggest that the United States cannot do the same."

"His choice is not unlike the choices that most German industrialists made in the Weimar Republic," one critic said of billionaire Charles Koch.

"Say no for Arizona," the Koch-backed group Americans for Prosperity tells the Democratic senator in a new ad.

"I did not come to Brown to study at an institution that promotes the presence of the Koch anti-science, anti-democratic ideology," wrote one student in a recent op-ed.

"There's no policy argument for it and no political justification," said one progressive group.