Washington ? The day before his inauguration, George W. Bush pointed to Karen Hughes at a staff meeting and told his other top advisers, “I don’t want any important decision made without her in the room.”

Bush’s order was strictly enforced. No major presidential conclusion, event or public utterance has escaped the eyes and ears of Hughes perhaps the most influential woman ever to have served a president.

But now the White House counselor is leaving the room. She ends an 18-month run at the White House on Monday, creating a Texas-sized vacuum in the orbit of presidential advisers.

“She won’t be here every single day to hear every single thing that’s going on in the White House, which she does now,” first lady Laura Bush said.

Hughes has been the president’s friend and alter ego, the aide he most trusts to sense what moves voters, particularly working women and mothers. She finishes his sentences. She laughs loudest at his jokes. She enforces his demand for discipline, rooting out aides who leak to the media or claim credit that could go to the president.

Hughes still plans to advise Bush from her home in Austin, Tex. A contract with the Republican Party could make the work more lucrative than her government salary of $145,000 a year.

At the White House, however, her departure threatens to undo a delicate balance of power.

Karl Rove, whose portfolio includes all things political and policy, will face less competition for Bush’s ear a point that worries some White House officials and GOP strategists.

Chief of Staff Andrew Card told Esquire Magazine he needed other aides to balance Rove, “but it won’t be easy. Karl is a formidable adversary.”

Such talk is dismissed by Hughes, Rove and Joe Allbaugh the “Iron Triangle” of advisers who helped Bush vault from the Texas statehouse to the White House.

Rove said his duties won’t change with Hughes’ departure, but life at the White House will. “I can no longer say, ‘Hey, I’ll see her in 15 minutes, and I can ask her that in a meeting.”‘

Hughes also plans to deliver speeches, and perhaps write a book about her experiences. Mrs. Bush wants help with her own book about children around the world.

“I won’t be able to run downstairs and get in the Oval Office,” Hughes said. “But I think I will be able to pick up a telephone and call the Oval Office and vice versa.”

The White House may give Hughes a secure telephone in Texas for her talks with Bush.

In her spacious corner office at the White House, Hughes is asked what the president will miss most about her. She reaches across a pile of papers and grabs a wooden lid from her desk only to have it slip from her grasp and land noisily.

“This unvarnished lid is here to remind me that I’m supposed to give him my unvarnished opinion,” Hughes said.

The scene might surprise Hughes’ critics, some of whom are on Bush’s team, who privately consider her loyal to a fault all but blind to her boss’ shortcomings.

One of her biggest fans, Mrs. Bush, said Hughes had a habit of beginning sentences by saying, “I’m just concerned that …” her way of gently correcting the president.

“I know my husband likes strong-willed women,” Mrs. Bush said. “Who wouldn’t if they had Barbara Bush as a mother?”

Hughes and her colleagues say other aides will fill her role, including communications director Dan Bartlett and press secretary Ari Fleischer.

What she loses in geography, Hughes said she hoped to gain in perspective by living closer to America’s pulse. Others say her influence will dwindle.

“Proximity is everything at the White House,” said Leon Panetta, chief of staff in the Clinton White House.