WASHINGTON (AP) – White House chief of staff Andy Card has resigned and will be replaced by budget director Joshua Bolten, President Bush announced Tuesday amid growing calls for a White House shakeup and Republican concern about Bush’s tumbling poll ratings.

Though there was no immediate indication of other changes afoot, the White House did not close the door on a broader staff reorganization. White House press secretary Scott McClellan said Bolten will have the authority to make personnel shifts if he deems them necessary, and he declined to say whether top aides, such as the two current deputy chiefs of staff, Joe Hagin and Karl Rove, would remain in place.

“All of us serve at the pleasure of the president,” McClellan said. “It’s premature to talk about any future decisions that may or may not be made.”

Bush announced the changes in a nationally broadcast appearance in the Oval Office.

“I have relied on Andy’s wise counsel, his calm in crisis, his absolute integrity and his tireless commitment to public service,” Bush said. “The next three years will demand much of those who serve our country. We have a global war to fight and win.”

Card, 58, stood stoically with his hands by his sides as Bush lauded his years of service through the Sept. 11 attacks, war and legislative and economic challenges. Gripping the podium, Card said in his farewell: “You’re a good man, Mr. President.” Card’s eyes were watery. Card said he looks forward to just being Bush’s friend. Bush then gave him five quick slaps on the back and the two walked out of the Oval Office together.

The president called Bolten, 51, a man with broad experience, both on Wall Street and in Washington, including the last three years as director of the Office of Management and Budget.

Alarmed by Bush’s declining approval ratings and unhappiness about the war in Iraq, Republicans have been urging the president to bring in new advisers with fresh ideas and energy. Bolten has been with Bush since his first campaign for the White House.

“The good news is the administration has finally realized it needs to change its ways, but the problems go far deeper than one staffer,” said Sen. Charles Schumer, D-N.Y. “Simply rearranging the deck chairs on the Titanic by replacing Andy Card with Josh Bolten without a dramatic change in policy will not right this ship.”

Bush gathered with members of his Cabinet in the Rose Garden at mid-morning after discussions about the war on terror. He ignored shouted questions from reporters about why he made the staff changes. Bush said he would deliver a speech on Wednesday about Iraq.

“We had a chance to honor two members of my Cabinet who won’t be with us much longer _ Secretary of the Interior Gale Norton, Chief of Staff Andy Card,” Bush said. “These two folks have served our country with distinction and honor. I’m proud to work side-by-side with them, and I’m proud to call them friend.”

To the public, Card may be best known as the aide who calmly walked into a Florida school room and whispered into Bush’s ear that America was under attack on Sept. 11, 2001. He was known for keeping his cool under pressure. When Bush’s father, then President George H.W. Bush, got sick at a banquet in Tokyo, aides and security officials ran toward the president. Card ran in the opposite direction, out the door to make sure the motorcade was ready to rush Bush away.

“Josh is a creative policy thinker,” Bush said. “He is a man of candor and humor and directness.”

The president said Card came to him in early March and suggested he should step down from the job he has held from the first day of Bush’s presidency.

Bush said decided during a stay at Camp David, Md., last weekend to accept Card’s resignation and to name Bolten as his replacemen.

Bolten is widely experienced in Washington, both on Capitol Hill as well as at the White House, where he was deputy chief of staff before becoming director of the Office of Management and Budget.

At a White House news conference last week, Bush was asked about rumors that a shake up in the White House staff was in the works. Bush said he was “satisfied with the people I’ve surrounded myself with.”

A veteran of the administrations of both President Ronald Reagan and the first President Bush, Card was widely respected by his colleagues in the Bush White House. They fondly called him “chief.”

He usually arrived at work in the West Wing by around 5:30 a.m. and frequently did not leave until 9 or 10 p.m.

Card plans to stay on the job until April 14, when the switch with Bolten takes place.

Associates said that Card, who was secretary of Transportation and deputy chief of staff for the first President Bush, had wanted to establish himself as the longest serving White House chief of staff. He would have had about another seven months to go to beat Sherman Adams, who served as President Dwight D. Eisenhower’s chief of staff and will keep the longest-serving distinction.

A recent AP-Ipsos Poll found that Bush’s job approval has dipped to 37 percent, his lowest rating in that poll.

Card did not immediately disclose his plans. His resignation immediately prompted questions about whether he would return to Massachusetts to run for governor or perhaps challenge Sen. Edward M. Kennedy, D-Mass., who currently faces no major GOP challenge for re-election this fall, or Sen. John Kerry, D-Mass., whom he helped defeat as the 2004 Democratic presidential nominee and who faces re-election in 2008.

Card, a Holbrook native, served as the state representative from his hometown from 1975 to 1982.