At the Democratic convention, practically every speaker has applauded President Obama for effecting major positive changes in American society. In a typical speech, Massachusetts Governor Deval Patrick trumpeted:

This is the president who delivered the security of affordable healthcare to every single American after 90 years of trying. This is the president who brought Osama bin Laden to justice, who ended the war in Iraq and is ending the war in Afghanistan. This is the president who ended “don’t ask, don’t tell” so that love of country, not love of another, determines fitness for military service. Who made equal pay for equal work the law of the land. This is the president who saved the American auto industry from extinction, the American financial industry from self-destruction, and the American economy from depression. Who added over 4.5 million private sector jobs in the last two-plus years, more jobs than George W. Bush added in eight.

San Antonio Mayor Julian Castro echoed these sentiments, adding that Obama “made a historic investment to lift our nation’s public schools and expanded Pell grants so that more young people can afford college” and “took action to lift the shadow of deportation from a generation of young, law-abiding immigrants called dreamers.”

For much of this, Obama indeed deserves credit—or blame, depending on one’s perspective. But in many cases Congress and the president acted together. In other cases—particularly the auto and financial bailouts—the Bush administration set the ball in motion and a Republican president would have almost surely kept it rolling. Some of the praise seems premature and exaggerated: Has Obama really “delivered the security of affordable healthcare to every single American,” as Patrick said? As for Afghanistan, Obama first escalated the war far beyond what either Bush or McCain advocated, and now he ominously suggests U.S. troops will remain there for another decade.

While they love to credit Obama for his supposed achievements, liberals often insist that the president cannot be blamed for current trends they dislike, especially relating to the war on terrorism, immigration, and the war on drugs.

This is, after all, the president who campaigned on closing Guantánamo, only to keep it open years after Republicans like Condoleezza Rice and Bush’s Defense Secretary Robert Gates said it should be closed. This is the president who escalated drone bombings in Pakistan, and bombed Yemen, Somalia, and Libya. This is the president who promised accountability and the rule of law, only to turn around and totally whitewash and immunize the previous administration for torturing war prisoners. This is the president who pledged to respect habeas corpus, only to fight the federal courts at every turn to shield presidential power, and who formalized his own authority to target American citizens for summary execution without judicial due process.

President Obama has accelerated the deportation of immigrants. He has vastly expanded the crusade against drugs—signing off on increased drug task force spending, ramping up raids of medical marijuana facilities by a factor of eight contrary to repeated promises he would stop them, allegedly arming Mexican drug cartels in a bizarre drug war strategy, making destruction of the opium trade central to his Afghanistan policy, and sending 200 Marines to Guatemala to combat trafficking.

Obama’s partisans would prefer to ignore all this. If cornered, they argue that Obama is just one man who does not run the entire administration, that he cannot halt the inertia of his predecessors’ policies, or that he lacks either the political power or the political capital to do what he would genuinely prefer to do.

This defense is almost exactly backwards. Admittedly, the president’s role is exaggerated in many areas. Commentators often wrongly attribute general moral, cultural, economic, and international trends to the president. For example, detractors have attacked the last two presidents for high gas prices that result from many factors beyond the White House’s domain.

Yet in most areas where Obama’s defenders attempt to pass the buck, the president enjoys wide latitude. As Commander-in-Chief, Obama can bring the troops home whenever he wants. He can refrain from ordering drone attacks. He can easily craft a national security agenda more compatible with civil liberties and human rights. As Chief Executive, he can cease the pot club raids. He can stop deportations, and has indeed been credited for doing so on the margins after scaling them up. He can pardon anyone jailed against his orders.

Nor does a political capital shortage explain the president’s behavior. Obama won in 2008 as the relative peace candidate. The American people expected him to reverse Bush’s precedents. In shaping detention policy, he could easily have pointed to poll results in 2009 showing more than 2/3 of Americans opposed indefinite detention. Even most Republicans want a far less invasive marijuana and Afghanistan policy than Obama has delivered.

Bush’s defenders acted much like Obama’s do today. They never relented in their mental contortions to shield their leader from blame—for horrific violence in Iraq, for prisoner abuse, for the incompetent and militaristic national response to Hurricane Katrina, for the steady expansion of domestic government, and for the financial collapse of 2008. Meanwhile, they commended Bush for every perceived blessing—the economic boom of the early 2000s, positive developments in Middle East politics, and the paucity of terrorist attacks on American soil since 9/11.

The hard truth is that presidents have much more power to cause harm than enrich or protect society. Bush indeed deserves blame for launching the war in Iraq. He does not deserve credit for creating millions of sustainable private sector jobs, but he did have a role in the easy credit boom that led to the bust.

As the head of the largest government—the largest legal agency of coercion and violence on earth—a president has massive power to inflict suffering. He can bomb any nation, jail or deport hundreds of thousands of people, order people tortured or executed, or unleash a nuclear holocaust. He can pick economic winners and losers, generally at the expense of taxpayers and consumers. He can impose new regulatory burdens on businesses. Or he can refrain from doing these things.

Often, the best a president can do is to stop doing harm. In his fourth year in office, Obama bears much if not total responsibility for most of what his military and law enforcement agencies do. On these issues in particular, the buck stops with him. If Obama’s supporters refuse to hold Obama accountable, they have no one to blame but themselves for America’s perpetual wars at home and abroad.