Presidents symbolically define their eras in ways that go far beyond their legislative victories or — to cite a recent example — their conspiracy-laden tweets. Their lives and their personal style shape American culture and often influence the ambitions of teenagers growing up in the shadow of their time in the White House.

So it was with John Kennedy’s glamor, Ronald Reagan’s cockeyed optimism, Barack Obama’s detached cool, and now, gulp, Donald Trump’s truncated definition of success.

Even Trump’s supporters would acknowledge that the 70-year-old president is a man of few interests beyond making money, imposing his brand on the world, relaxing in the company of billionaires, and playing golf. As The Washington Post’s David Fahrenthold revealed during the campaign, Trump’s idea of altruism was buying a six-foot portrait of himself at a charity auction with money from the Trump Foundation.

Everything about our gold-plated president, from his Cabinet choices to his disdain for conflict-of-interest rules, signals that the meaning of life, is “He who dies with the most toys wins.” Even Trump’s Twitter insults directed at The New York Times (“dwindling subscribers and readers”) and Arnold Schwarzenegger (“fired by his bad pathetic ratings”) suggest that his only measure of anything is the bottom line.

In sharp contrast to Trump, the presidency of Franklin Roosevelt encouraged a sense that Americans were bound together in common cause. That sense of shared obligation carried a nation of 130 million through the Depression and World War II. When FDR gave a “Fireside Chat” on radio, half of America listened in, a figure that puts Trump’s audience for his address to Congress (48 million) to shame.

Ninety-year-old Charles Peters, whose new book “We Do Our Part” is being published this week, is among the last of the generation whose lives were molded by Franklin Roosevelt. Part joyful memoir, part shrewd political analysis and part insightful cultural criticism, “We Do Our Part” is the summation of Peters’ admirable life in the public sphere. He was one of the guiding spirits of the Peace Corps in the 1960s and the founder of the enduring, quirky, nonideological liberal magazine, the Washington Monthly.

All the gushy adjectives in the prior book description should come with an asterisk since I am proudly biased. My own journalistic career was forged by the Washington Monthly in the 1970s and Charlie Peters — one of the most influential figures in my life — helped guide me beyond knee-jerk partisanship and smug liberal superiority.

An important message

But even if I fail the test of journalistic objectivity, I sincerely believe that “We Do Our Part” is an important book arriving at the necessary moment. Although Peters acknowledges the segregation and limited opportunities for women in the America of his youth, he also mourns the loss of an era “when most of us viewed each other as human beings … [and] when there was more concern for public service and less for personal gain.”

Hard as it is to believe in a 21st century context, the purpose of going into the upper levels of government during the New Deal was to do good and have a stimulating life rather than to simply set yourself up to get rich in the private sector afterward. Yes, there were prominent exceptions like former FDR aide Tommy Corcoran who became a Washington legal fixer. But as Peters points out in a spritely review of Corcoran’s checkered career, the influence-peddling route to riches was not widely followed in Washington until the 1970s and 1980s.

Peters, who served in the Army stateside during World War II, offers a pointed reminder of how the universal male military draft, both in wartime and during the 1950s, broke down class-based social barriers. He unearths a John F. Kennedy speech from his 1946 House race in which the future president talked passionately about how World War II veterans “miss the close comradeship, the feeling of interdependence, that sense of working together in a common cause.”

“We Do Our Part” (the title was New Deal slogan) is much more than simply an elegy to the 20th century. Writing in the shadow of Trump’s victory, Peters, a proud son of West Virginia, offers a keen understanding of where the Democrats went wrong in scorning the kind of people in Appalachia that he grew up with.

‘Legitimate concerns’

Ticking off issues like crime, guns, abortion and the environment, Peters declares that he still leans to the liberal side on these policy debates. But, he cautions, “in every case, however, I find myself troubled by many of my fellow liberals’ failure to understand the legitimate concerns of the other side.”

As a columnist who covered the debate over NAFTA during the Clinton years, I remember the confident certainty of the liberal free traders who scorned the insular attitudes of anyone opposed to globalization. It sadly never occurred to most Clintonites that opposition to change was often more about blue-collar workers’ sense of identity than lost wages.

It is rare that a writer at 90 retains the ability to harness the sweep of history and to aptly apply it to the current debates over the future of America in an age of trumpery. So I am tempted to call “We Do Our Part” Charlie Peters’ bravura valedictory statement. But the book is so good — and Charlie is so indelible and enduring — that I nurture the hope of a sequel.

Roll Call columnist Walter Shapiro is a veteran of Politics Daily, USA Today, Time, Newsweek and the Washington Post. His book on his con-man great-uncle was just published: “Hustling Hitler: The Jewish Vaudevillian Who Fooled the Fuhrer.” Follow him on Twitter @MrWalterShapiro.