Doris Kearns Goodwin is a first-class American presidential historian. Her new book, Leadership: Lessons from the Presidents for Turbulent Times, could not be better timed. American voters went to the polls this week in mid-term elections that, like the 2016 presidential race, showed a divided nation. At at the time of writing Republican President Donald Trump had lost control of the House of Representatives but continued to hold the Senate.

Goodwin cemented her reputation with the brilliant Team of Rivals (2005), which explored Abraham Lincoln’s masterful political management in constructing a cabinet of senior Republicans who had competed with him for the party’s presidential nomination in 1860.

She has written extensively on the four great presidents at the heart of her new book: Lincoln, Theodore Roosevelt, Franklin D. Roosevelt and Lyndon Baines Johnson.

She details how each of them was shaped in adversity. She shows how, despite their scarring experiences, they performed courageously at times of extraordinary challenge for the American republic.

A theme throughout is how the powers of the Oval Office can be turned to the resolution of great issues for the national interest and the public good. In Goodwin’s skilful telling, leadership is composed of equal measures of vision and purpose.

Make no mistake. Lincoln, Theodore Roosevelt, his distant cousin Franklin and Johnson were formidable politicians.

Lincoln, whose horrific childhood could easily have been in Mark Twain’s The Adventures of Huckleberry Finn, could be thoroughly partisan at times; Teddy Roosevelt was prone to outbursts of aggressive nationalism; FDR could be duplicitous, especially in dealing with supporters; and LBJ played his politics in the style that he had learned in the rough house of Texas Democratic primaries.

But these presidents were unifiers, understanding the value of consistency in speaking to the American people and, in so doing, appropriating the power of language.

John F. Kennedy wrote in Profiles in Courage, for which he won a Pulitzer prize in 1957, that Winston Churchill had harnessed the ­English language and sent it off to war. The same could be said of Lincoln and FDR, while language also proved decisive for Theodore Roosevelt in settling the Great Coal Strike of 1902 and LBJ in pursuing landmark civil rights reform in 1964.

Words matter. Words can be deployed for seriously good outcomes or monstrously evil intent, as we have seen recently.

These presidents were unifiers, understanding the value of consistency in speaking to the American people and, in so doing, appropriating the power of language.

Consider, from Goodwin’s book, this passage on transformational leadership as Lincoln crafts the Emancipation Proclamation:

For the first time, the president yoked Union and slavery into a single, transformative, moral force. Some three and a half million blacks in the South who had lived enslaved for generations were promised freedom. Eighty words in one sentence would supplant legislation on property rights and slavery that had governed policy in the House and Senate for nearly three-quarters of a century.

Contrast the inspiration of the Emancipation Proclamation with the toxic campaign language that has characterised this week’s mid-term elections, whether on the border, at the rallies or in the digital ether.

In issuing the Emancipation Proclamation, Lincoln expanded the powers of the presidency (which had been deliberately limited by the founding fathers).

So, too, did Theodore Roosevelt in resolving the protracted and destructive Great Coal Strike. The president, who lost his wife and his mother on the same day, understood that he had no constitutional authority to intervene. However, this did not stop him quietly enlisting the assistance of JP Morgan to set up a meeting with the coal barons and the president of the emerging United Mine Workers, John Mitchell.

The meeting was at Roosevelt’s temporary Washington residence, where he was convalescing after an accident. The coal barons behaved badly, as coal barons routinely do, especially one George Baer.

Where Roosevelt produced a winning hand was in having the talks recorded by stenographers and eventually having the transcript published. As winter approached, American opinion shifted decisively behind the president’s crisis management and the miners’ cause.

This book is a profoundly thoughtful assessment of the most powerful democratic office yet created. The word “from” in the title is important. There are indeed lessons here for today’s political leaders.

“Certainly, the statements of George Baer did little to bolster the owner’s cause,” Goodwin writes.

At one point he even insisted that the rights of the working men would be better protected not by labor agitators but by “Christian men to whom God in his infinite wisdom has given control of the property interests of the country”.

His statement, which was reproduced in the press, created widespread condemnation and mockery. ‘‘The divine right of kings was bad enough”, scoffed one Boston paper, “but not so intolerable as the doctrine of the divine right of plutocrats”

For FDR, the first days of his presidency in March 1933, at the height of the Great Depression, were the most perilous. He responded with characteristic vigour. Crippled years earlier by polio, he nonetheless injected an energy into American national government that had been sorely lacking.

Goodwin writes of FDR’s distinctive personality, which enabled him to lead by example.

Franklin Roosevelt’s compelling and authentic performance on Day One had been decades in the making. The young boy who had concealed an ugly gash on his forehead beneath his cap so as not to worry his ailing father, had fashioned no mere mask but an outward demeanour of serenity, confidence, and relaxation, however grave the maelstrom that encircled him.

FDR’s New Deal filled a legislative void and staved off the collapse of the American banking system. In so doing, he began a revival in the confidence of Americans in their government.

As did Johnson, introducing civil rights legislation in congress in 1964 in the wake of the assassination of Kennedy and continuing repression of African-Americans in the south.

Trump heads an administration that is one roiling campaign rally, as the mid-terms have shown. This has undoubted electoral appeal, especially for the Trump base, but it leaves the American republic polarised and poisoned and less capable of acting intelligently and meaningfully in Washington, DC, or anywhere else.

Johnson was not renowned for eloquence. But in addressing a joint session of congress he took hold of Theodore Roosevelt’s bully pulpit with both hands.

“There is no Negro problem. There is no southern problem. There is only an American problem. And we are met here tonight as Americans — not as Democrats or Republicans — we are met here as Americans to solve that problem.

“There is no issue of state rights or national rights. There is only the issue of human rights.”

LBJ had suffered electoral reversal in Texas and humiliation as vice-president at the hands of the Kennedys. But on the great issue of civil rights, he more than rose to the occasion.

Goodwin has contributed much to our appreciation of the American presidency and Leadership adds to her impressive record of scholarship.

This book is a profoundly thoughtful assessment of the most powerful democratic office yet created. The word “from” in the title is important. There are indeed lessons here for today’s political leaders.

Politically astute US presidents have been healers, from Lincoln’s second inaugural address to Bill Clinton in Oklahoma City through to George W. Bush at the mosque in the wake of 9/11.

Trump heads an administration that is one roiling campaign rally, as the mid-terms have shown. This has undoubted electoral appeal, especially for the Trump base, but it leaves the American republic polarised and poisoned and less capable of acting intelligently and meaningfully in Washington, DC, or anywhere else.

Stephen Loosley is a visiting fellow at the United States Studies Centre at the University of Sydney.

Leadership: Lessons from the Presidents for Turbulent Times

By Doris Kearns Goodwin

Viking, 480pp, $49.99 (HB), $35 (PB)