Former Secretary of State Alexander Haig, who served Republican presidents and ran for the office himself, has died.

Haig died Saturday at Johns Hopkins Hospital in Baltimore from complications associated with an infection, his family said. He was 85.

President Obama praised Haig as a public servant who "exemplified our finest warrior-diplomat tradition of those who dedicate their lives to public service. He enjoyed a remarkable and decorated career, rising to become a four-star general and serving as Supreme Allied Commander of Europe before also serving as Secretary of State."

Secretary of State Hillary Clinton said Haig "served his country in many capacities for many years, earning honor on the battlefield, the confidence of presidents and prime ministers, and the thanks of a grateful nation."

"I think of him as a patriot's patriot," said George P. Shultz, who succeeded Haig as the country's top diplomat in 1982.

"No matter how you sliced him it came out red, white and blue. He was always willing to serve."

The four-star general served as a top adviser to three presidents and had presidential ambitions of his own. President Richard Nixon appointed him White House chief of staff in 1973. In that role, Haig helped the president prepare his impeachment defense and handled many of the day-to-day decisions normally made by the chief executive.

In later years, Haig spoke of Nixon in cautious terms.

"I found with President Nixon -- and I'm sure there are similarities today -- that these are very political beings," he told Fox News in 1998. "They wouldn't be in that office if they weren't politically astute."

Haig later served as secretary of state under President Ronald Reagan.

In the chaotic hours following the attempted assassination of Reagan in March 1981, Haig uttered what became his most famous statement.

"As of now, I am in control here, in the White House," Haig said.

The remark misrepresented the line of presidential succession and it made it easier for critics to portray Haig as a usurper of power.

In 2001, Haig defended his remark.

"Everybody in that room was very familiar with the fact that this was not a discussion about transition, but rather authority within the executive branch," he said.

Haig quit the Reagan Cabinet after a year-and-a-half -- disgusted, he said, with bureaucratic infighting.

"You can't have the State Department putting out one line and the Defense Department another line and the White House yet another line," he told Fox News in 2002.

In 1988, Haig campaigned for the GOP presidential nomination but was forced to drop out before the end of February.

He published two memoirs, profited in the private sector, and spent much of his later years fiercely defending his unique, storied, and intensely controversial role across four decades of public service.

Born Dec. 2, 1924, in the Philadelphia suburb of Bala Cynwyd, Alexander Meigs Haig spent his boyhood days dreaming about a career in the military. With the help of an uncle who had congressional contacts, he secured an appointment to the U.S. Military Academy at West Point in 1943.

After seeing combat in Korea and Vietnam, Haig -- an Army colonel at the time -- was tapped by Henry Kissinger to be his military adviser on the National Security Council under President Richard M. Nixon. Haig "soon became indispensable," Kissinger later said of his protege.

Nixon promoted Haig in 1972 from a two-star general to a four-star rank, passing over 240 high-ranking officers with greater seniority.

The next year, as the Watergate scandal deepened, Nixon turned to Haig and appointed him to succeed H.R. Haldeman as White House chief of staff. He helped the president prepare his impeachment defense -- and as Nixon was preoccupied with Watergate, Haig handled many of the day-to-day decisions normally made by the chief executive.

On Nixon's behalf, Haig also helped arrange the wiretaps of government officials and reporters, as the president tried to plug the sources of news leaks.

About a year after assuming his new post as Nixon's right-hand man, Haig was said to have played a key role in persuading the president to resign. He also suggested to President Gerald Ford that he pardon his predecessor for any crimes committed while in office -- a pardon that is widely believed to have cost Ford the presidency in the 1976 against Democrat Jimmy Carter.

Years after serving as one of Nixon's closest aides, Haig would be dogged by speculation that he was "Deep Throat" -- the shadowy source who helped Washington Post reporters Bob Woodward and Carl Bernstein break the Watergate story. Haig denied it, repeatedly, and the FBI's Mark Felt was eventually revealed as the secret source.

Following Nixon's resignation, Haig stayed with the new Ford administration for about six weeks, but then returned to the military as commander in chief of U.S. forces in Europe and supreme allied commander of NATO forces -- a post he held for more than four years. He quit during the Carter administration over the handling of the Iran hostage crisis.

Haig briefly explored a presidential run in 1979, but decided he didn't have enough support and instead took a job as president of United Technologies -- his first job in the private sector since high school.

When Ronald Reagan became the 40th president of the United States, Haig returned to public service as Reagan's secretary of state, and declared himself the "vicar of American foreign policy."

His 17-month tenure was marked by turf wars with other top administration officials -- including Defense Secretary Caspar Weinberger and national security adviser William Clark.

Two months into the new administration, Haig was portrayed as pounding a table in frustration when the chairmanship of a crisis management team went to Bush. Despite the clashes, Haig received high praise from professional diplomats for trying to achieve a stable relationship with the Soviet Union.

He also conducted shuttle diplomacy between the British and Argentine governments in an unsuccessful attempt to avert a war over the Falkland Islands.

In his book, Haig said he had concluded during a 1982 trip to Europe with the president that the "effort to write my character out of the script was under way with a vengeance." He resigned days later.

Describing himself as a "dark horse," Haig sought the Republican presidential nomination for the 1988 elections. On the campaign trail, he told supporters about his desire to "keep the Reagan revolution alive," but he also railed against the administration's bulging federal deficit -- calling it an embarrassment to the Republican Party.

Haig dropped out of the race just days before the New Hampshire primary.

During his career in public service, Haig became known for some of his more colorful or long-winded language. When asked by a judge to explain an 18 1/2-minute gap in one of the Nixon White House tapes, Haig responded: "Perhaps some sinister force had come in."

And later, when he criticized Reagan's "fiscal flabbiness," Haig asserted that the "ideological religiosity" of the administration's economic policies were to blame for doubling the national debt to $2 trillion in 1987.

Haig is survived by his wife of 60 years, Patricia; his children Alexander, Brian and Barbara; eight grandchildren; and his brother, the Rev. Francis R. Haig.

Fox News' James Rosen and The Associated Press contributed to this report.