Heidi N. Moore is a digital-media strategy consultant based in New York and a former editor, columnist and reporter for publications including The Guardian U.S. and The Wall Street Journal.

Let’s get one thing out of the way: Yes, Donald Trump makes a cameo appearance in Lucas Graves’s new book on the importance of fact-checking, and no, it’s not flattering. In this timely book, “Deciding What’s True: The Rise of Political Fact-Checking in American Journalism,” Graves inevitably addresses Trump and his truthfulness. He notes that PolitiFact’s judgments on the 2016 race found that only 5 percent of Trump’s statements ranked more than “Half-True” by mid-2015, a far lower rate than any of his opponents. (His truthfulness hasn’t changed much since then.)

Graves drily concludes that “fact-checking appears to do a good job of catching out those politicians who exhibit a flagrant disregard for truth.” But he shies away from branding any politician a liar, noting that fact-checkers never use the term. “This would require knowing someone’s heart,” he writes. He casts aspersions on very few people, and that civility offers a balm to the weary political soul this year.

As Graves traces the rise of fact-checking, he also illustrates the decline of political discourse into a steady drip of misinformation. Politicians are attached to their narratives, on which their careers depend. The traditional gatekeepers — daily political journalists — are, in his description, frequently hemmed in by their attachment to objectivity. These journalistic customs may be why Hillary Clinton, in each debate, referred viewers to live fact checks of her opponent run by her own staff. But the impact of fact-checking may be limited anyway because of the partisanship of readers who often prefer their Facebook feeds for news because they affirm their preexisting political opinions.

In the 1980s, journalists fact-checked Ronald Reagan, “who came to the White House with a well-established reputation for error and exaggeration,” in Graves’s words. Newspapers, particularly The Washington Post, truth-squadded every one of Reagan’s news conferences until readers demonstrated so little concern that the paper backed off, according to former Post reporter Walter Pincus: “It’s up to the Democrats to catch people, not us. We would quote both sides.”

"Deciding What's True: The Rise of Political Fact-Checking in American Journalism," by Lucas Graves (Columbia Univ.)

In 1992, however, the impulse came back: Major networks and newspapers launched teams to fact-check advertising in the presidential race between George H.W. Bush and Bill Clinton. By 2004, a George W. Bush administration official mocked a reporter for being part of the “reality-based community,” which he said was divorced from the political power of “history’s actors,” who create their own realities. In 2012, Nobel Prize laureate Paul Krugman talked about the “post-truth” era of politics.

Some of the strongest opponents of political fact-checking are top editors and reporters who were trained in a determinedly objective practice of journalism, reporting both sides of an issue but taking neither. (The academic Jay Rosen has derided this as the “view from nowhere.”) Graves points out that then-New York Times editor Jill Abramson argued that fact-checking in a straight news article would cause readers to see the paper as a combatant, not an arbiter, in political battles. Graves acknowledges the uneasiness that journalists and fact-checkers alike have. Fact-checking was not intended “to clean up politics,” a goal that those involved in the process saw “as obviously futile and possibily inappropriate,” Graves writes.

But there’s still an urge to free reporters of studious objectivity, Graves suggests. Journalism risks becoming less relevant the more it sticks to an unrealistic bird’s-eye view that doesn’t mediate events or interpret for the reader. “Ultimately, the most lasting impact of the fact-checking movement may be in giving political reporters new license to embrace the muckraking, reformist impulse that is both so vital and so tenuous in professional journalism,” Graves concludes.

One of the most important reasons for the news media to embrace some rabble-rousing is this: While journalists agonize over objectivity, who is left to bear witness? History needs a record of truth, though it doesn’t really matter who provides it. “No permanence, no perseverance in existence, can even be conceived of without men willing to testify to what is,” Hannah Arendt wrote in her essay “Truth and Politics.”

In Graves’s view, fact-checkers are the ones to police the political process. He focuses on the history of three outlets — PolitiFact, FactCheck.org and The Post’s Fact Checker — but also includes nearly every other news outlet in his anecdotes. Fact-checkers work parallel to newsrooms: to keep both politicians and political journalists accountable, in Graves’s view. He says that at the first fact-checking summit in 2014, many attendees “saw themselves as political reformers.” But, interestingly, any organization demonstrating a clear political preference — from Media Matters to Fox News — is excluded from gatherings of fact-checkers, who regard themselves as nonpartisan. In some cases, fact-checker organizations and newspapers that maintain fact-checking editors and reporters forbid their staffers from any political involvement.

It’s hard to envy the fact-checkers their work. Correcting the facts of history happens only with considerable discomfort on all sides: To his credit, Graves never pretends in this fairly brief book that fact-checking is easy. It’s time-consuming; it encounters resistance from politicians, readers and journalists alike; and oh, by the way, no one can quite agree on what a fact is. “Facts can be subjective,” The Post’s fact-checker, Glenn Kessler, tells Graves. The discussion of what constitutes a fact forms a big chunk of the book, and deservedly so: Nuance is the hardest part of fact-checking work.

Another major problem with fact-checking that the book sidesteps is the burden on the reader. Google announced recently that it had created an algorithm to favor fact-checking pieces, but even so, readers not only have to read the news but then seek out fact checks of what they just read. It’s a lot of work — more than most people are willing to put in.

Another core problem is the power — or lack of power — of facts themselves. Since facts are subjective, their ability to change minds may be more limited than we think, particularly in elections like this one where fact checks — fine, immaculate work by well-trained professionals — have taken a back seat to the rush of emotion. Political campaigns rely on intangibles: charisma, credibility, communication style. As far as politics go, facts can’t fix us.

Graves’s book will appeal to those who are interested in politics and journalism and the intersection of the two, which is to say, the entirety of the Internet commenter class. For those looking for context and a sense of how we got here, it is a foundational work.

Deciding What’s True
The Rise of Political Fact-Checking in American Journalism

By Lucas Graves

Columbia. 324 pp. $30 paperback