WASHINGTON — As he introduced his new choice for secretary of health and human services in the East Room this week, President Obama turned his head from right to left, but he wasn’t looking at the audience. He was reading from two teleprompters, strategically set up outside the tight television camera shot.

When he was done, the teleprompters quietly began retracting down to the floor. As she stepped forward to make her own remarks, his nominee, Kathleen Sebelius, seemed momentarily surprised.

“Don’t mind the little—— “ Mr. Obama said with a smile.

“It’s disappearing!” she joked.

Presidents have been using teleprompters for more than half a century, but none relied on them as extensively as Mr. Obama has so far. While presidents typically have used them for their most important speeches to the nation — an inauguration, a State of the Union or an Oval Office address — Mr. Obama uses them for everyday routine announcements, and even for the opening statement at his news conference.

He used them during a visit to a Caterpillar plant in Peoria, Ill. He used them to make brief remarks at the opening of his “fiscal responsibility summit.” He used them during a visit to the Interior Department to discuss endangered species, even as he recalled a visit to some national parks as an 11-year-old. “That was an experience I will never forget,” he said, reading from the teleprompter.

For Mr. Obama, a teleprompter means message discipline, sticking close to his intended words. Every president uses prepared remarks, of course, often reading from paper or note cards. But while some of his predecessors liked to extemporize, Mr. Obama prefers the message to be just so. After all, he is a bestselling author who has had a hand in writing many of his major speeches, so his aides say he feels a certain fidelity to the crafted text.

Michael Waldman, who was President Bill Clinton’s chief speechwriter, said Mr. Obama is one of the few politicians who is able to use a teleprompter effectively. “If he were just reading something someone handed him, and didn’t understand what it said, that would be one thing,” Mr. Waldman said. “But I don’t think anybody doubts that he’s expressing his own thoughts.”

Yet Bradley A. Blakeman, a former White House aide to President George W. Bush and a Republican strategist, said the teleprompter makes Mr. Obama look robotic. “He is extremely scripted, and he is cautious to the max and afraid of gaffes,” Mr. Blakeman said. When answering questions without a script, Mr. Blakeman said, “his speech is very halted, and you can see him take a lot of time to think about what he’s going to say.”

Presidents have had a love-hate relationship with teleprompters for generations. Aides tried to get Harry S. Truman to use them, but he scowled that it would make him look insincere. Dwight D. Eisenhower became the first president to put them to use, but he was not a fan either, grousing to aides about having to “use that damn teleprompter.”

Some have had particularly bad experiences. In 1993, when Mr. Clinton addressed Congress to promote his health-care plan, the wrong speech was fed into the teleprompter. It took George Stephanopoulos and other aides a nightmarish seven minutes to fix the problem while Mr. Clinton winged it. Some thought he did better without the script.

Four years later, it almost happened again. A last-minute change to the State of the Union in 1997, made during the motorcade to the Capitol, somehow caused the entire text to be formatted as a single endless paragraph. As Mr. Clinton mounted the lectern, aides rushed through the text trying to reinsert paragraph breaks, finishing just as he started.

Even when Mr. Clinton had the right speech in the teleprompter, though, he often drifted so far from the prepared text that the operator controlling the tempo of the scrolling struggled to figure out where the president might reconnect with the script. “The guy was like a fighter pilot, with a bead of sweat on his head, trying to land on the carrier,” recalled Mr. Waldman.

And then there was Mr. Bush’s speech to the United Nations in 2002 about the looming confrontation with Iraq. After a tough debate among his advisers, Mr. Bush agreed to seek a new Security Council resolution, but when the speech scrolled across the teleprompter, the key line was missing. Advisers panicked when he kept going without saying the line, but then Mr. Bush noticed its absence and ad-libbed it.

The trouble was, he said he would seek “the necessary resolutions,” plural, which later became an issue when the Europeans pressed him to come back to the Security Council for a second resolution before going to war.

Mr. Obama never used a teleprompter until his keynote address at the 2004 Democratic convention, but he relied on them regularly on the campaign trail last year. After one speech, he was spotted in a tense exchange with an aide, a flash of temper his spokesman later attributed to a teleprompter malfunction. The machines became a point of attack in the blogosphere, with one critic even setting up a Web site called teleprompterpresident.com to post videos of the candidate stumbling over words when he did not use the machines.

The continued presence of the teleprompters after the inauguration was widely noticed when he used them to read an opening statement at his news conference. The teleprompters then lowered to the floor when it came time to answer reporters’ questions.

The White House dismissed questions about the use of the machines. “Whether one uses note cards or a teleprompter, the American people are a lot more concerned about the plans relayed than the method of delivery,” said Bill Burton, a spokesman. “This is not always true of the media.”

Kevin Sullivan, Mr. Bush’s last White House communications director, said he was surprised to see the teleprompters used so frequently, and said that it risks making Mr. Obama look staged. When the camera angle widened during the announcement of Ms. Sebelius’s nomination, he noted, she was obscured by the teleprompter.

“This is the most gifted and effective communicator of our generation,” Mr. Sullivan said. “I find it hard to believe he needs it.”

But Nicolle Wallace, another former Bush White House communications director who carefully studied Mr. Obama when she worked for Senator John McCain during last year’s campaign and admires Mr. Obama’s speaking skills, said the new president should stick with success.

“I’d say, for a guy known around the world for being as effective as he is at communicating, he shouldn’t change a thing,” she said. “If that’s what works for them, that’s what he should do.”

Photo by Doug Mills/The New York Times