The Red and the Blue: The 1990s and the Birth of Political Tribalism. By Steve Kornacki.Ecco; 512 pages; $29.99.

A S HE WOULD be the first to tell you, Newt Gingrich is a politician of ideas—big, strange and sometimes terrible ideas. In 1981, during his second term in Congress, he introduced a bill to enable America to make the Moon a state. In one of his dozens of books, he mused about bringing dinosaurs back to life. During his presidential campaign in 2012, he proposed making poor children janitors at their schools. His most enduring idea may also have been his worst: he figured out how to break American politics. If Steve Kornacki’s “The Red and the Blue” has a villain, it is Mr Gingrich.

Mr Kornacki is that rarest of creatures: a thoughtful and informative cable-news personality. His perceptive book traces the roots of contemporary America’s political dysfunction back to Mr Gingrich’s heyday in the 1990s.

When he entered the House of Representatives in 1979, as the first Republican ever elected from Georgia’s 6th district, Democrats had controlled the chamber for 24 years. That is not because mid-century America was flagrantly left-wing. It was because the parties had not yet sorted themselves into near-uniform ideological blocs.

The realignment that began when Lyndon Johnson, a Democratic president, signed the Civil Rights Act of 1964 was still in its infancy. Southerners remained heavily Democratic, a legacy of the Confederacy’s defeat in the American civil war by a government led by Abraham Lincoln, a Republican. They joined north-eastern liberals, union members and non-whites to form a rickety but large coalition. The largely north-eastern “Rockefeller Republicans” were often more liberal than conservative Southern Democrats.

A degree of comity prevailed, which Mr Gingrich took as weakness—a sign that his fellow Republicans were content to remain in permanent minority. Richard Nixon had won two presidential elections overwhelmingly in 1968 and 1972 (Ronald Reagan would do the same in 1980 and 1984). Why, Mr Gingrich wondered, could Republicans not replicate that strength in Congress? As Mr Kornacki explains, he realised that the key lay “in nationalising congressional politics through confrontations with the ruling Democrats”.

In other words, stop treating Congress as a place to legislate and compromise; instead, make it an arena for permanent, all-out partisan warfare, waged both in the legislative chamber and on the proliferating 24-hour news channels. It was a simple notion, really, but one that required overweening ambition and utter indifference to institutional norms—both of which Mr Gingrich had in abundance. The energised minority caught the complacent majority flat-footed; having spent more than a decade laying the groundwork, Republicans took back the House in 1994, and Mr Gingrich became the first Republican Speaker since 1955.

As Mr Gingrich was amassing power in Congress, a wily, ambitious Democratic governor from Arkansas was circling the ring. Bill Clinton considered running for president in 1988, but that was the year in which Gary Hart’s promising campaign sank when reporters caught him cavorting on a boat with a young woman who was not his wife. Rumours of extramarital dalliances had long dogged Mr Clinton; he decided discretion was the better part of valour.

His party was in an odd fix: strong locally but spent nationally. Organised labour and urban machine-politics were weakening, white southerners were flowing away. Reagan had turbocharged Nixon’s southern strategy, appealing to socially conservative, working-class whites with a mixture of easy bonhomie and racist dog-whistles (“young bucks” supposedly buying steaks with food stamps, “welfare queens” abusing public aid).

Depending on your perspective, Mr Clinton was his party’s saviour or its murderer. He became the nominee in 1992 only after threading a narrow path through a field weakened when the favourite, Mario Cuomo, declined to run—as did other luminaries, including Bill Bradley, Sam Nunn and Lloyd Bentsen. He would save the Democrats by making them nationally competitive again. Yet many left-leaning Democrats never forgave Mr Clinton for his triangulation—which they saw as capitulation to the Republican premise that government is best when it does least—or for constantly frustrating his party’s left flank.

Fresh from a victory in the Gulf war, meanwhile, George H.W. Bush seemed to be unbeatable to the left. But he was vulnerable on the right, and faced a surprisingly strong challenge from Pat Buchanan, a rabble-rousing populist. Mr Kornacki expertly shows how Mr Buchanan’s rise pre-figured the election of 2016. His insurgent campaigns—he ran for president twice as a Republican and later for Ross Perot’s Reform Party—hit many of the same themes that resounded in the most recent race: opposition to free trade and immigration, with strong appeals to white racial grievance. “Illegal drugs are coming across the border,” he thundered at the Republican convention of 1996. “Illegal immigration is soaring!”

Donnie from Queens, you’re on the air!

In 2000 the rag-tag Reform Party attracted a rival champion—another media-savvy operator with malleable principles, one Donald Trump. Mr Trump had left the Republican Party, he said, because “they are just too crazy right.” He derided Mr Buchanan as “an anti-Semite. He doesn’t like the blacks. He doesn’t like the gays.” He considered running with Oprah Winfrey, calling “non-politicians…the wave of the future”. In the end, the Reform Party disintegrated into farce: its more prominent members included David Duke, a Klansman, and Lenora Fulani, a “black nationalist Marxist”. Mr Trump walked away.

But he proved prescient about the country’s yen for non-politicians in office. Perhaps that susceptibility was always there—stemming from a bedrock belief in the wisdom of ordinary people, and suspicion of government—but during the 1990s the barriers that had kept it in check came down. The machines that powered the 20th-century Democratic Party, in unions and big cities, stalled. Mr Gingrich’s zeal for sharp partisan confrontation turned the Republican Party into a fractious entity much better at winning elections than at governing responsibly.

Along with the decline of trusted, unifying information sources—and the ascent of those that reinforced viewers’ prejudices—the weakened but consolidated parties bequeathed by the 1990s left America primed for takeover by a demagogue. Mr Kornacki’s book does readers a service by showing them how America got here. Where it goes now seems beyond anybody’s ken.