Barbara McQuade is a professor from practice at the University of Michigan Law School and a former U.S. attorney for the Eastern District of Michigan.

When Donald Trump became president, some wondered whether he would pivot from his unconventional and bombastic campaign style and become more “presidential.” In fact, the presidency has not changed Trump. Trump has changed the presidency.

Susan Hennessey and Benjamin Wittes explore Trump’s role as disrupter of his office in their new book, “Unmaking the Presidency: Donald Trump’s War on the World’s Most Powerful Office.” Both are senior fellows at the Brookings Institution and editors at Lawfare, a blog devoted to national security matters. While much ink has been devoted to documenting Trump’s presidency, this book goes deeper by placing his presidency in historical context and offering an insightful and sobering look at how Trump may change the office forever.

Referring to Trump’s idiosyncratic style of governing as “the expressive presidency,” Hennessey and Wittes write, “The personal nature of his presidency was a function of his imagining the presidency as a platform for his personal expression, not as an executive office whose job is actually to run things.”

The authors catalogue various aspects of Trump’s leadership style, including his decision-making process, use of speech to influence the public, disregard for government ethics and conduct of foreign affairs, among other things, to demonstrate his rejection of norms. They describe Trump’s presidency as “devoid of process and fundamentally about the vanity of the individual.” The book cites Trump’s view of law enforcement as a shield for allies and a weapon against enemies. He refuses any scrutiny of his conduct by Congress, courts or the free press. He conducts foreign policy on “whim and tantrum.”

Changing the presidency is not necessarily a bad thing, and Hennessey and Wittes describe how the office has evolved over its history. For example, Theodore Roosevelt and Woodrow Wilson changed how presidents communicate with the public. Roosevelt used the presidency as a bully pulpit from which to reach Americans directly. Wilson upended the tradition of providing a written State of the Union to Congress, instead delivering it in person so that his message would be heard directly by the people. Both practices have stuck.

The process of nominating federal circuit court judges has also changed over time. Whereas presidents once gave great deference to U.S. senators to recommend nominees for federal judgeships in their states, the tradition did not stop Jimmy Carter from “consciously dismantling this norm” to promote diversity on the bench. Ronald Reagan then capitalized on this break from historical practice to appoint more judges with conservative ideologies. The merit of that change is in the eye of the beholder.

One key feature of Trump’s expressive presidency is his assault on truth. Noting that The Washington Post documented 2,000 lies in Trump’s first year in office alone, Hennessey and Wittes describe a “persistent presidential disinformation campaign.” He uses Twitter, friendly media outlets and campaign rallies to repeat simple and memorable mantras, such as “witch hunt” or “no obstruction,” eschewing actual arguments and instead allowing proxies to take up his case and fill in the gaps. In addition to outright lies, Trump also frequently contradicts himself, “creating a kind of house-of-mirrors effect; one can never be sure which direction to look or what is real and what is illusion,” and conditioning “large segments of the public to accept the notion that if a presidential lie wasn’t a crime, then it was no big deal.”

The risk of a president who lies consistently, of course, is that over time, he loses credibility with the American public and foreign allies. Dishonesty erodes not only Trump’s effectiveness, but also the effectiveness and prestige of the office itself. When allies cannot rely on America’s word, we cannot build coalitions. As Hennessey and Wittes put it, “The author of ‘The Art of the Deal’ cannot make deals, for who would rely on his word in a negotiation?”

The authors point out that it is tempting to think that when Trump’s term ends, “everything will snap back to normal,” but this assumption ignores the condition that led to his election in the first place. Trump is a product of an era of political tribalism. In this atmosphere of intense polarization, “in which hating and defeating the other side is the only virtue,” we can expect Trump’s conduct to influence future presidents. “It seems imprudent to bet against some enterprising politician attempting a more sophisticated Version 2.0 of the entire undertaking,” Hennessey and Wittes write.

Like all presidents, at his inauguration, Trump took an oath promising to use his powers to promote the public good. He then promptly proceeded to act in his self-interest. While legal reforms are often discussed as ways to heighten the guardrails against future abuse, such reforms have limitations because a president unconstrained by his oath “will find ways to abuse the mammoth powers of the presidency.”

The framers of the Constitution created a presidency with virtues and flaws. As the authors note: “The American presidency is a package deal. You can’t have its nimbleness and capacity for decisive action without its potential for misuse and its dependency on good faith. You can’t have its unity without its capacity for impunity. You can’t have its independence without its capacity for going rogue.”

But our structure of government also provides a solution. As Hennessey and Wittes write, if certain presidential norms matter to the American public, then it is up to us to defend them. The only real check on presidential abuses of power is the “need to go back to the electorate every four years for ratification.” The process of nominating judges changed because the existing norm went undefended. But when Franklin Roosevelt obtained a third and then a fourth term, Congress and states responded with the 22nd Amendment, limiting presidents to two terms.

If Trump is defeated in 2020, his norm-breaking will signal a failed presidency, making it less likely that successors will replicate his conduct. But if we reward Trump with a second term after his abusive wielding of power, the office will be forever changed.

Unmaking the Presidency

Donald Trump's War on the World's Most Powerful Office

By Susan Hennessey and Benjamin Wittes

Farrar, Straus and Giroux. 418 pp. $28