During the 1980 election, an up-and-coming Washington think tank called the Heritage Foundation undertook a massive task: to examine the federal government from top to bottom and produce a detailed, practical conservative policy vision.

The result, called Mandate for Leadership, epitomized the intellectual ambition of the then-rising conservative movement. Its 20 volumes, totaling more than 3,000 pages, included such proposals as income-tax cuts, inner-city “enterprise zones,” a presidential line-item veto, and a new Air Force bomber.

Despite the publication's academic prose and mind-boggling level of detail, it caused a sensation. A condensed version -- still more than 1,000 pages -- became a paperback bestseller in Washington. The newly elected Ronald Reagan passed out copies at his first Cabinet meeting, and it quickly became his administration’s blueprint. By the end of Reagan’s first year in office, 60 percent of the Mandate’s 2,000 ideas were being implemented, and the Republican Party’s status as a hotbed of intellectual energy was ratified. It was a Democrat, Daniel Patrick Moynihan, who would declare in 1981, “Of a sudden, the GOP has become a party of ideas.”

The story of the conservative movement that has come to dominate the Republican Party over the last four decades is inextricably intertwined with the story of the Heritage Foundation. In that time, it became more than just another think tank. It came to occupy a place of special privilege -- a quasi-official arm of GOP administrations and Congresses; a sponsor of scholarship and supplier of legislation; a policy base for the party when out of power. Heritage has shaped American public policy in major ways, from Reagan’s missile-defense initiative to Clinton’s welfare reform: Both originated as Heritage proposals. So, too, did the idea of a universal health-care system based on a mandate that individuals buy insurance. Though Heritage subsequently abandoned it, the individual mandate famously became the basis of health-care reforms proposed by Massachusetts Governor Mitt Romney and President Barack Obama....