Goldwater Institute

From their website:
Founded in 1988 with the blessing of the late Senator Barry Goldwater, the Goldwater Institute’s mission is to advance freedom and protect the Constitution.
As a non-​profit organization funded solely by individual donations, we stand on principle, not politics. Headquartered in Phoenix, Arizona, we believe in the power of the states to restore America to the founding principles that made it a beacon of opportunity, prosperity, and freedom.
We research and develop ideas that help states use their constitutional powers to protect their citizens’ liberties. And when governments overstep their constitutional authority, the Goldwater Institute defends citizens in court.
The Goldwater Institute is staffed by the brightest minds in economics, education, and constitutional law. An advisory panel of Senior Fellows adds breadth of knowledge and expertise.
The Goldwater Institute is a 501c (3) organization and accepts only private donations, not government funding or contract research. We have contributors from all 50 states and no single contributor provides more than five percent of revenue.