WASHINGTON -- If President Obama tuned in to the past week's bracing debate on Capitol Hill about terrorism, executive power, secrecy and due process, he might have recognized the arguments his critics were making: He once made some of them himself.
Four years into his tenure, the onetime critic of President George W. Bush finds himself cast as a present-day Mr. Bush, justifying the muscular application of force in the defense of the nation while detractors complain that he has sacrificed the country's core values in the name of security.
The debate is not an exact parallel to those of the Bush era, and Mr. Obama can point to ways he has tried to exorcise what he sees as the excesses of the last administration. But in broad terms, the conversation generated by the confirmation hearing of John O. Brennan, his nominee for C.I.A. director, underscored the degree to which Mr. Obama has embraced some of Mr. Bush's approach to counterterrorism, right down to a secret legal memo authorizing presidential action unfettered by outside forces.
At the same time, a separate hearing in Congress revealed how far Mr. Obama has gone to avoid what he sees as Mr. Bush's central mistake. Testimony indicated that the president had overruled his secretaries of state and defense and his military commanders when they advised arming rebels in Syria.
With troops only recently home from Iraq, Mr. Obama made clear that he was so intent on staying out of another war against a Middle East tyrant that he did not want to be involved even by proxy, especially if the proxies might be questionable.
Critics on the left saw abuse of power, and critics on the right saw passivity.
The confluence of these debates suggests the ways Mr. Obama is willing to emulate Mr. Bush and the ways he is not. In effect, Mr. Obama relies on his predecessor's aggressive approach in one area to avoid Mr. Bush's even more aggressive approach in others. By emphasizing drone strikes, Mr. Obama need not bother with the tricky issues of detention and interrogation because terrorists tracked down on his watch are generally incinerated from the sky, not captured and questioned. By dispensing with concerns about due process, he avoids a more traditional war that he fears could lead to American boots on the ground.
"I'd argue the shift to more targeted action against A. Q. has been a hallmark of Obama's approach against terrorism, whereas Iraq was Bush's signature decision in his global war on terror," said Benjamin J. Rhodes, a deputy national security adviser to Mr. Obama, using the initials for Al Qaeda.
The Brennan hearing highlighted the convoluted politics of terrorism. Conservatives complained that if Mr. Bush had done what Mr. Obama has done, he would have been eviscerated by liberals and the news media. But perhaps more than ever before in Mr. Obama's tenure, liberals voiced sustained grievance over the president's choices.
"That memo coming out, I think, was a wake-up call," said Christopher Anders, senior legislative counsel of the American Civil Liberties Union. "These last few days, it was like being back in the Bush days."
"It's causing a lot of cognitive dissonance for a lot of people," he added. "It's not the President Obama they thought they knew."
The dissonance is due in part to the fact that Mr. Obama ran in 2008 against Mr. Bush's first-term policies but, after winning, inherited Mr. Bush's second-term policies.
By the time Mr. Bush left office, he had shaved off some of the more controversial edges of his counterterrorism program, both because of pressure from Congress and the courts and because he wanted to leave behind policies that would endure. He had closed the secret C.I.A. prisons, obtained Congressional approval for warrantless surveillance and military commissions, and worked to close the prison at Guantánamo Bay, Cuba.
So while Mr. Obama banned harsh interrogation techniques, he preserved much of what he inherited, with some additional safeguards; expanded Mr. Bush's drone campaign; and kept on veterans of the antiterrorism wars like Mr. Brennan. Some efforts at change were thwarted, like his vow to close the Guantánamo prison and to try Sept. 11 plotters in civilian court.
"These are the same issues we've been grappling with for years that are uncomfortable given our legal structures and the nature of the threat, but the Obama team is addressing these issues the same way we did," said Juan Carlos Zarate, who was Mr. Bush's deputy national security adviser for combating terrorism.
Peter D. Feaver, a Duke University professor and former Bush national security aide, said Mr. Obama "believed the cartoon version of the Bush critique so that Bush wasn't just trying to make tough calls how to protect America in conditions of uncertainty, Bush actually was trying to grab power for nefarious purposes."
"So even though what I, Obama, am doing resembles what Bush did, I'm doing it for other purposes," Mr. Feaver added.
Others said that oversimplified the situation and ignored modifications that Mr. Obama had enacted. "It is a vast overstatement to suggest that President Obama is channeling President Bush," said Geoffrey R. Stone, a University of Chicago law professor who hired a young Mr. Obama to lecture there. "On almost every measure, Obama has been more careful, more restrained and more respectful of individual liberties than President Bush was."
"On the other hand," Mr. Stone added, "at least in his use of drones, President Obama has legitimately opened himself up to criticism for striking the wrong balance" between civil liberties and national security.
Particularly stark has been the secret memo authorizing the targeted killing of American citizens deemed terrorists under certain circumstances without judicial review, a memo that brought back memories of those in which John Yoo, a Justice Department official under Mr. Bush, declared harsh interrogation legal.
That broad assertion of power, even with limits described by administration officials, combined with the initial White House refusal to release even a sanitized summary of the memo touched off protests from left and right. Some called Mr. Obama a hypocrite. But Mr. Yoo himself saw it differently, arguing in The Wall Street Journal that the memo, whatever the surface similarities to his own, betrayed a flawed vision because it presented the issue in law enforcement terms rather than as an exercise of war powers.
Michael V. Hayden, the C.I.A. director under Mr. Bush, said that if Mr. Obama learned one thing from experience it should be that controversial programs require public support to be sustained. "Err on the side of being open, at least with Congress," he said. "Otherwise you're going to find yourself in a politically vulnerable position."
For four years, Mr. Obama has benefited at least in part from the reluctance of Mr. Bush's most virulent critics to criticize a Democratic president. Some liberals acknowledged in recent days that they were willing to accept policies they once would have deplored as long as they were in Mr. Obama's hands, not Mr. Bush's.
"We trust the president," former Gov. Jennifer Granholm of Michigan said on Current TV. "And if this was Bush, I think that we would all be more up in arms because we wouldn't trust that he would strike in a very targeted way and try to minimize damage rather than contain collateral damage."
But some national security specialists said questions about the limits of executive power to conduct war should not depend on the person in the Oval Office.
"That's not how we make policy," said Douglas Ollivant, a former national security aide under Mr. Bush and Mr. Obama and now a fellow at the New America Foundation. "We make policy assuming that people in power might abuse it. To do otherwise is foolish."
This article originally appeared in The New York Times.