For nearly 30 years, the Republican Party has increasingly resembled a religion, with Ronald Reagan as its deity. Party leaders endlessly quote him, and every GOP presidential nominee until Donald Trump ran on a platform they thought was barely changed from Reagan’s 1980 campaign.No wonder conservative talk radio icon Rush Limbaugh calls our 40th president “Ronaldus Magnus”: Ronald the Great.

This religion’s creed—let’s call it Reaganism—is simple. Government and taxes are bad, private entrepreneurship and supply-side economics is good. Social conservatism and unofficial endorsement of Christianity is essential to national well-being. Around the world, America should speak loudly, carry the biggest stick and never be afraid of using it. Proclaim and practice these truths and political success will be yours.

This canon has been repeated for so long that it seems self-evidently true to Republicans and movement conservatives. But it’s simply not the sum of what Reagan believed.

I discovered this while researching my new book on Reagan’s life. I learned that election returns show Americans don’t want what Reaganism’s high priests are preaching. More crucially, I learned that everything I thought I knew about Reagan was wrong—that Reaganism misrepresents Reagan’s own views. ...

Reagan’s early conservative talks before he rose to national fame during Goldwater’s bid for the presidency in October 1964 argued that certain government social programs weren’t needed to meet “humanitarian aims.” He would criticize bureaucrats who bossed people around or programs that gave aid to people who didn’t need it. He did not, however, join other conservatives and say New Deal programs were unconstitutional or an improper thing for government to do. Nor, if the programs genuinely met a legitimate need, did he criticize them for costing too much.

Quite the contrary. I just about fell off my chair in the Reagan Library when I heard him say this in a 1958 speech: “In the last few decades we have indulged in a great program of social progress with many welfare programs. I’m sure that most of us in spite of the cost wouldn’t buy many of these projects back at any price. They represented forward thinking on our part.”

He repeated similar sentiments in every speech I listened to, even saying in 1961, “Any person in the United State who requires medical attention and cannot provide for himself should have it provided for him.” That year, he supported an alternative to Medicare called the Kerr-Mills Act that gave federal funds to states so they could help poor senior citizens pay for medical care, even writing to a longtime friend that “if the money isn’t enough I think we should put up more.”

Reagan did not change his stripes as he became conservatism’s hero, and continued to preach his own unique conservative vision. He told viewers of the October 1964 “Time for Choosing” speech endorsing Goldwater, the speechthat made him a national political star, that conservatives were for “telling our senior citizens that that no one in this country should be denied medical care for lack of funds.” He campaigned for governor of California saying talk “in America of left and right” was “disruptive talk, dividing us down the center.” He said his “Creative Society,” intended to be a non-bureaucratic alternative to Lyndon Johnson’s “Great Society,”wasn’t “some glorified program for passing the buck and telling people to play Samaritan and solve their problems on their own while government stands by to hand out Good Conduct ribbons.” And when he became governor, he pushed through a then-record tax increase after his efforts to “cut, squeeze, and trim” government could not balance the budget.

He didn’t alter his views when he ran for and became president, either. ...