WASHINGTON — As White House chief of staff, Rahm Emanuel was the one to bring the hammer down on Sidney Blumenthal.

Secretary of State Hillary Rodham Clinton wanted to hire Blumenthal, a loyal confidant who had helped her promote the idea of a “vast right-wing conspiracy” more than a decade ago. But President Barack Obama’s campaign veterans had not forgotten his role in spreading harsh attacks against their candidate in the primary showdown with Clinton last year.

So Emanuel got hold of Clinton, said Democrats informed about the situation, and explained that bringing Blumenthal on board was a no-go. The last thing the administration needed, he concluded, was a polarizing figure sowing dissension and drama in the ranks. In short, Blumenthal was out.

Perhaps nothing illustrates how far Emanuel has come than that conversation last month. Sixteen years ago, it was Clinton, then first lady, who helped have Emanuel demoted as a senior official in Bill Clinton’s White House after he ruffled feathers with his aggressive style. Now all these years later, it is Emanuel telling Clinton what she cannot do as a member of the Cabinet.

Seven months after moving into his office in the West Wing, Emanuel is emerging as perhaps the most influential White House chief of staff in a generation. But with his prominence in almost everything important in Washington comes a high degree of risk.

As the principal author of Obama’s do-everything-at-once strategy, he stands to become a figure of consequence in his own right if the administration stabilizes the economy and financial markets, overhauls the health care system and winds down one war while successfully prosecuting another.

If things do not go well — and right now Obama’s political popularity is declining, his health care legislation is under conservative assault, the budget deficit is at an eye-popping level and Afghanistan remains volatile — it is Emanuel whose job will be on the line before Obama’s.

“He’s about to be tested; he’s spinning a lot of plates over there and he breaks a lot of china,” said Joel Johnson, a close friend and fellow veteran official of the Clinton White House. “They’ve had some good success early on, but they’ve got a number of major pieces of the agenda in the queue, and it’s going to be really difficult.”

The caricature of Emanuel as a profanity-spewing operative has given way to a more nuanced view: as a profanity-spewing operative with a keen understanding of how to employ power on behalf of a new president with relatively little experience in Washington.

Although relentlessly deferential to the president, Emanuel is clearly more chief than staff. While some predecessors husbanded their authority, lest it be diluted, friends said Emanuel believed the more someone used power, the more power that person had.

He knows how to pull all the levers of influence in Washington — raising money, mobilizing interest groups and harvesting the latest policy ideas from research groups. At the same time, Emanuel’s relentless campaign-style approach sometimes leaves some colleagues worried they spend too much time reacting to events.

At times, it seems as if Emanuel is White House chief of staff, political director, legislative director and communications director all rolled into one. He has fingers in almost every decision, like who gets invited to social events at the White House and how to shape economic and foreign policy.

He carries a notecard in his pocket with a list of things to accomplish and marks them off obsessively. He requires Cabinet secretaries and all West Wing departments to submit written reports each week and returns them with terse notes in the margins.

As negotiations intensified on health care recently, Emanuel was a constant presence on Capitol Hill — one day alone, he was there 8.5 hours before returning to the White House to tend to other duties.

“He can juggle 20 or 25 things in one day, in part by delegating and in part by picking only the things that matter,” said Transportation Secretary Ray LaHood, a Republican congressman recruited by Emanuel to serve in the Cabinet.

‘THE A.D.D. RAHM’

Where Obama is known for cool detachment, Emanuel presses until the breaking point, then presses some more.

“The president has a zenlike quality,” said Obama’s senior adviser, David Axelrod. “Rahm is a pile driver.”

Attention has focused on Emanuel’s larger-than-life personality, but it is his operating style that matters more to Obama at this crucial juncture. What comes through in interviews with about 60 people in the White House, on Capitol Hill and around Washington is an intense engagement built on a series of testosterone-driven aphorisms:

“Put points on the board.”

“In politics, you’re either pitching or catching.”

“A man never stands as tall as when he is on all fours kissing” rear ends.

In other words, take what victories you can, stay on the offensive and do not be afraid to stroke big egos to advance the president’s agenda.

Emanuel, 49, starts his day shortly after 5 a.m., when he swims at the YMCA and then hits the House gymnasium to pick up intelligence from colleagues from his days in Congress. At 7:30 a.m., he gathers top White House officials in his office and meets the full senior staff in the Roosevelt Room at 8:15 a.m. He then sees the president alone in the Oval Office for 10 minutes, a private session repeated at the end of each day.

Aides estimate Emanuel talks with 50 people a day by telephone and sends hundreds of e-mail messages. Phone calls often last a minute or two, just long enough to deliver a point or extract information. E-mail messages are often a word or two.

“It seems like he has a 72-hour day,” said Sen. Charles E. Schumer, D-N.Y.

But Emanuel casts his net widely, from lawmakers and lobbyists to journalists and corporate executives. When he took over the chief of staff’s office — an office that, he makes a point of telling visitors, is 8 square feet larger than the vice president’s — he brought a telephone list of 6,000 names that crashed White House software.

“I’ve heard more from Rahm in six months than I heard from Andy Card in six years, and Card’s daughter worked for me,” said former Rep. Tom Davis, R-Va., referring to a chief of staff under President George W. Bush.

Peter R. Orszag, director of the Office of Management and Budget, noted one day this month that he had been with Emanuel in meetings from 8:15 a.m. until noon but still had three telephone calls and a dozen e-mail messages from him later that day.

But if Emanuel flits from subject to subject, he tries to manage his own short attention span.

“There’s the Rahm who’s frenetic, the A.D.D. Rahm, the ‘Ari Emanuel’ Rahm making a thousand phone calls a day and BlackBerrying one-word messages,” said John D. Podesta, Bill Clinton’s last chief of staff, referring to Emanuel’s Hollywood-agent brother. “But then there’s a corporate Rahm that extends his decision-making and authority.”

The people he extends that to include two deputy chiefs of staff, Jim Messina and Mona Sutphen, and aides like Sarah Feinberg and Sean Sweeney. He also relies heavily on Pete Rouse, a senior presidential adviser, and Phil Schiliro, the legislative director.

Emanuel presides over a White House where people are defined by whether they went through the fires of the campaign. Emanuel himself did not. When Obama invited longtime aides like Axelrod and Robert Gibbs, the press secretary, to Camp David recently, Emanuel was not included.

He gets along well with most other members of the Obama team, including Axelrod, a longtime Chicago friend who served as a witness at his wedding. But as a head-knocking addition to the tightly knit “no drama Obama” world, Emanuel has almost inevitably been in the midst of some tensions. Emanuel was wary of Valerie Jarrett, the president’s close friend, joining the White House staff. In the intervening months, the two “have spent a lot of time working at that” relationship and “get along well now,” Podesta said.

But when a New York Times Magazine profile of Jarrett last month explored the old scratchiness, White House officials said the normally calm Obama erupted with anger. An informal edict went out: no more cooperating with staff profiles. As a result, Emanuel declined a formal interview for this article.

FEAR IN HIS WAKE

Whatever intrigue exists inside the White House, Emanuel, who once dreamed of becoming House speaker, spends as much time monitoring the intrigue on Capitol Hill.

When the House was taking up a war spending bill in June, Emanuel noticed a Republican ally had yet to vote. With one minute left on the vote clock, he called the ally, Rep. Peter T. King of New York. “There’s only one minute to go in the vote,” Emanuel said into voicemail. “I’m waiting for you.”

King, who did vote for the bill, laughed as he recounted the story. “I had this crazy guy from the White House watching me,” he said.

Emanuel’s hand could be seen in many fights Obama has won, including the economic stimulus package, the bank bailout and the budget bill, which passed the House by a wider majority than any in 10 years.

When Obama decided to eliminate the F-22 fighter jet, Emanuel called his old friend William M. Daley, a former commerce secretary, to ask him to generate an audience in Chicago for Defense Secretary Robert M. Gates to announce the move. Then Emanuel called more than 20 members of Congress. “He’s been so good to me, when he said, ‘We need you on this,’ I said fine,” recalled a Democratic senator who asked not to be identified describing a private conversation.

Emanuel still trades on a reputation sealed years ago as a ferocious operative, a reputation that, by most accounts, is dated. While he remains a tough, foul-mouthed scrapper, he is more likely these days to give a dog dish to a senator who got a new puppy (as he did to Kent Conrad this summer) than send a dead fish to an enemy (as he did two decades ago as a brash young campaign aide.

“There are negotiations with him all the time,” said Sen. Ben Nelson, D-Neb. “You can be as flexible or inflexible as he is.”

Or as Gibbs put it: “He doesn’t snarl, snap his teeth and chew people up and spit them out.”

But the fear that he might works to his advantage. When Rep. Gerald E. Connolly, D-Va., led freshman lawmakers to the White House to express concern about health care legislation, he was struck that Emanuel listened respectfully. Emanuel’s reputation set a low bar so that, in effect, Connolly said, the message was: “I could eat you alive but I didn’t. Don’t you feel better now?”

That is not to say Emanuel does not still play hardball. When Sen. Jon Kyl of Arizona, the Republican whip, criticized Obama for spending too much, Cabinet secretaries sent a letter to his state’s governor, Jan Brewer, a Republican, asking what stimulus money she did not want.

Rep. Darrell Issa of California, the ranking Republican on a House oversight committee, vowed to investigate Emanuel’s involvement, and in an interview he questioned the sincerity of Emanuel’s outreach to Republicans. “He’ll smile and at the same time he flips you the bird,” Issa said. “The best way to describe Rahm is that he’s a brass-knuckle Chicago politician.”

While jousting with the right, Emanuel has tried to impose order on the left, dispatching Messina to weekly meetings with liberal interest groups called the Common Purpose Project, a tactic adopted from the Bush White House. Emanuel showed up this month amid internal tension over health care. Asked about liberal advertisements aimed at Democrats in conservative districts, he delivered an obscenity-laced tirade about the senselessness of attacking each other, participants said.

To say he has inserted himself into the heart of negotiations with Congress might understate it. When Obama spoke with congressional leaders last month to get an update on health care before heading overseas, Sen. Harry Reid of Nevada, the Democratic leader, asked, “But Rahm is going to stay here, right?”

THE BOSS

Any White House blends political operatives with policy wonks in a sometimes-uneasy relationship. In this White House, they have given themselves nicknames — the Aspen Institute policy people versus the Tammany Hall political people. Emanuel is the undisputed boss of Tammany Hall. But he sometimes challenges the Aspen Institute on its turf.

Emanuel is more involved in domestic and foreign policy than outsiders realize, colleagues said. After Treasury Secretary Timothy F. Geithner stumbled in rolling out a new banking policy, Obama told Emanuel to step in, and he met for an hour each day with the economic team to develop a workable policy.

Emanuel also helped formulate a plan expanding access to community colleges. And when the economic team wrote new financial industry rules, officials said he insisted on breaking out limits on the credit card industry so they could be passed separately and right away.

In national security, officials said Emanuel had been a player on issues central to the Obama presidency — Afghanistan, Pakistan, Iran, the Middle East and, to some extent, Iraq and Russia. He has been a force behind the administration’s opposition to Israeli settlement expansion, drawing fire from some Israel supporters.

After a last-minute decision to have the president go to Saudi Arabia yielded no tangible results, Emanuel pushed to ensure that future foreign trips had “deliverables,” or achievements secured in advance.

Emanuel’s win-the-day mentality, so shunned by the Bush team, can make for a reactive White House. Where Bush’s aides prided themselves on sticking to plans, Emanuel constantly adjusts. Aides said they went home at night thinking they knew the next day’s plan, only to discover after his 7:30 a.m. meeting with top advisers that the plan had been ripped up.

It can have a whipsaw effect. At one staff meeting this summer, Emanuel and colleagues discussed whether rising deficits justified scaling back stimulus spending, one participant said. A week or so later, the discussion had turned 180 degrees. Concerned the stimulus was not working, the group discussed a second stimulus plan.

But Emanuel insists on discipline. When an environmental policy decision was leaked, he lashed out at a staff meeting, saying anyone in the room who thought they were smarter than the president should go into the Oval Office and tell him.

“Whatever that image, inside the administration it is like a family,” Orszag said. “You can disagree in private, but you’re not going to air the disagreements publicly and you’re not going to undercut your sibling — or you’ll pay for it at the dinner table.”