His guests were just about everything George H.W. Bush had never been, and never could be: ideological, hard edged and spoiling for a partisan revolution. It was the spring of 1989, and Newt Gingrich, a young congressman from Georgia, had been elected the House Republican whip, a key leadership post in the Washington of the 41st president. Mr. Bush, who was more comfortable in the fading moderate precincts of the Republican Party, didn't know Mr. Gingrich well, but the perennially hospitable president invited him and Vin Weber, the Minnesota Republican congressman who had managed Mr. Gingrich's whip campaign, down to the White House for a beer. The conversation was pleasant, but the visitors felt there was something Bush was not quite saying. Mr. Weber decided to put the question to the president directly.

"Mr. President, you've been very nice to us," Mr. Weber said as they were preparing to leave. "Tell us what your biggest fear is about us."

"Well," Mr. Bush answered, "I'm worried that sometimes your idealism will get in the way of what I think is sound governance." In the most polite way possible, in a single sentence, Mr. Bush had summarized his anxiety that when politics and principle clashed, politics was going to win.

Mr. Weber recalled that he appreciated the president's use of the word "idealism" -- he hadn't said "extremism" or "partisanship," though that was what he meant. The two congressmen represented a harsh new kind of politics that would, in five years' time, lead to the first Republican takeover of the House in four decades. By then George Bush would be back in Texas, a one-term president done in by the right wing of his own party -- a conservative cabal that rebelled against Mr. Bush's statesmanlike deal with Democrats to raise some taxes in exchange for spending controls to rein in the deficit. [...]

As an 18 year old, he volunteered for hazardous duty as a carrier-based naval aviator in World War II. As commander in chief, nearly half a century later, he, with the Soviet leader Mikhail Gorbachev and building on the work of presidents of both parties down the decades, ended the deadliest standoff in human history, the Cold War. Before he got to the White House, a nuclear Armageddon between America and the Soviet Union was always a possibility; after him, it was unthinkable.

On the home front, his 1990 budget agreement codified controls on spending and created the conditions for the elimination of the federal budget deficit under his successor, Bill Clinton. He negotiated the North American Free Trade Agreement, signed the Americans with Disabilities Act and passed historic clean-air legislation. It's virtually impossible to imagine a Republican president doing so much today.

It's an inescapable fact of history, though, that as Bush struggled to govern like Ike, the world around him was beginning to resemble a Joe McCarthy rally. In the Bush years conservative Republicans girded for total war, talk radio was on the rise, cable news shows were busy turning politics into a kind of professional wrestling for wonks, and populists such as Ross Perot and Pat Buchanan -- forerunners, in their way, of Donald J. Trump -- were waiting for their chance to pounce. (Mr. Bush did think an overture from Lee Atwater, his campaign manager, to consider Mr. Trump for the 1988 vice-presidential nomination the most puzzling of notions. "Strange," Mr. Bush told his diary. "Unbelievable.")