CARTHAGE, TENN., JUNE 29 -- Sen. Albert Gore Jr. (D-Tenn.) today became one of the youngest candidates ever to seek a major party presidential nomination as he pledged from the courthouse steps of his home town to "restore the rule of law and respect for truth and common sense to the White House."

"Some have asked me, 'Why don't you wait,' " said Gore, 39, who would be the youngest president in the nation's history if he were inaugurated in January 1989 at age 40.

"History itself is speeding up, with events cascading upon events . . . . We no longer have the luxury of waiting. We must accept the challenge of the future now, rekindle the spirit of America, and regenerate a sense of national purpose which only a president can define."

Gore, who once described himself as a "raging moderate," brings a handsome political pedigree to the race. He is a second-generation politician (Albert Gore Sr. served 32 years in the House and Senate), was educated at Harvard, owns a 72-acre farm here, ran a small business, spent six years as a journalist, served eight years in the U.S. House and has spent two in the Senate -- and is the first Vietnam veteran in his party to seek the presidency.

As a college student, Gore was active in Sen. Eugene McCarthy's antiwar presidential campaign of 1968. He volunteered for the Army when he was on the verge of being drafted, in part because his father was in the thick of a reelection battle in which his opposition to the war had become a liability. The elder Gore lost the 1970 election; the son served as an Army journalist.

In his announcement today, Gore read the names of eight Carthage (pop: 2,600) natives who died in Vietnam. "Their memory challenges us to ensure a strong national defense and create a better world," he told a crowd of several thousand under a scorching midmorning sun.

Gore delivered his speech from same spot his father had launched his career half a century earlier, and a few miles from the farms father and son own. He spoke of reducing the federal deficit, investing in education, cleaning up the environment, attacking homelessness, drug abuse and crime, providing child care and expanded medical coverage, reducing Third World debt and taking advantage of a "possibly historic opportunity" to achieve an arms control pact.

"For the first time in at least a generation, the Soviet Union has a leader who combines youthful energy and innovation with experience," he said. "And the free world urgently needs a leader who can match him, test him, bargain with him . . . ."

Gore also said that "Americans in every region and of both political parties have been shaken by the betrayal of public trust, the theft of public money, the shredding of public documents and the dishonesty of public officials." He promised, as president, to fire any official who steals or lies to Congress.

Gore is the sixth Democrat to formally join the 1988 presidential race and the first southerner. In the historical passages of his speech, he skipped the presidencies of Lyndon B. Johnson and Jimmy Carter and harkened back to Woodrow Wilson, whom he described as a "son of the South." Wilson, a Virginia native, was governor of New Jersey before being elected president.

Gore's southern credentials are also a bit tenuous. He has lived all his life in the Washington, D.C., area, and attended St. Albans School. His farm here is mostly a summer retreat for him, his wife, Tipper, and their four young children.

Perhaps to compensate, he has made a yeoman effort to stay in touch with his "roots," holding about 1,800 town meetings -- an average of 180 a year -- across his district and state in the past decade.

Gore's vast appetite for meeting with the voters is part of reputation for hard work and vigor that many here think is his greatest political asset. "We need some young blood up there in Washington," said Elmer Brown, 60, a farmer who works at the local hardware store.

"People are tired of having a president who falls asleep at meetings," said Rep. Thomas J. Downey (D-N.Y.), one of four congressmen who joined Tennessee Gov. Ned McWherter and senior Sen. Jim Sasser at the announcement.

Gore's youth has a down side: It creates a "stature problem" that may explain his inability to attract much political support outside his home state in the two months he has been campaigning. His staff is relatively inexperienced in national politics and his effort to build momentum as a "regional favorite son" has so far been stunted by the shadow of Sen. Sam Nunn (D-Ga.), who has said he will not decide whether to join the race until September.

"If Sam doesn't run, that will free up a great deal of political and financial support to come our way," said Nathan Landow, a Bethesda developer who heads an organization of Democratic fund-raisers called IMPAC 88.

Gore's decision to run came this spring, shortly after he met with members of the IMPAC group and impressed some of them, especially with his detailed mastery of arms control issues. Before his meeting with the group in mid-March, Gore had said he had no intention of running in 1988. After 17 members pledged to support him, he reversed himself and entered the race. Gore played down any cause-and-effect in the sequence of events.

Gore's voting record during his decade in Congress has been on the liberal side for a southerner -- he has lifetime ratings of 80 percent from the AFL-CIO and 65 percent from Americans for Democratic Action. He has made his mark by becoming a specialist in such relatively arcane issues as the "greenhouse effect" and organ transplants.

In the House and Senate, Gore has played an active role on arms control issues. During Reagan's first term he worked with Rep. Les Aspin (D-Wis.) and others to find a middle ground between the administration and Democrats who were eager to advance the arms control agenda. He helped orchestrate compromises that kept the MX missile alive and promoted the single-warhead Midgetman missile.

At a speech in an American Legion Hall later in the day in Manchester, N.H., where Gore picked up the endorsement of 22 prominent Democratic activists, he said the United States has the responsibility to keep the sea lanes open in the Persian Gulf.

Gore's wife is a controversial public figure. Recently, she has led a parents' crusade against violence and sexually explicit material in rock lyrics and music videos.