RONALD REAGAN HAS traveled a long and bumpy road to the summit. It has been a personal odyssey, marked by many changes in position, in strategy and -- perhaps most importantly -- in the rhetoric he uses to describe the Soviet Union.

In a characterization that said as much about the distance he has traveled as it does about his Soviet counterpart, Reagan recently described Soviet leader Mikhail Gorbachev as "a reasonable man" who understands "that if we both want peace, there'll be peace."

These words were far different from those Reagan used on Jan. 29, 1981, at his first presidential news conference, when he said the Soviets are bent on "the promotion of world revolution and a one-world socialist or communist state." He added that "the only morality they recognize is what will further their cause, meaning that they reserve unto themselves the right to commit any crime, to lie, to cheat in order to attain that."

Since then, much has changed. Key members of Reagan's staff have been replaced, and he has waged a reelection campaign during which political strategists and U.S. allies pushed for a more conciliatory approach to the Soviets.

Some advisers say Reagan, who cannot run for reelection, also recognizes that time is running out on his chance for progress in the superpower relationship. At the same time, they say the Soviets realize that Reagan has the standing to win Senate ratification of an arms-control treaty.

"Where he's going with his present approach and what he's likely to get out of it just isn't possible to know at this point," a longtime Reagan adviser said. "It isn't clear that he's going anywhere or is likely to get anything. But what is clear is that the president has learned that dealing with the Russians takes more than denunciations."

The president's discourse on communist morality at his initial news conference was vintage Reagan. It reflected a world view formed in the early days of a political career that began with accusatory battles against Communists in post-World War II Hollywood, then tempered in the 1964 conservative crusade of Republican presidential candidate Barry Goldwater and finally sharpened in a 1976 primary campaign in which Reagan accused incumbent President Gerald R. Ford of weakening U.S. defenses in the face of a Soviet buildup.

The challenge to Ford failed narrowly, but not before Reagan had demonstrated that even a conservative Republican president was vulnerable if accused of dealing too gently with the Soviet Union.

Four years later, with U.S. suspicions heightened by the Soviet invasion of Afghanistan, Reagan was elected president after a campaign in which he accused President Jimmy Carter of making a "shambles" of the nation's defenses and being "totally oblivious" to the Soviet drive for world domination.

"The response from the administration has been one of weakness, inconsistency, vacillation and bluff," Reagan told the Veterans of Foreign Wars convention in the same speech in which he proclaimed the Vietnam War "a noble cause."

Reagan came to office as the most outspokenly anti-Soviet U.S. president of modern times. In an interview March 3, 1981, with Walter Cronkite, the new president defended his harsh descriptions of Soviet leaders and said of a possible summit, "We could talk a lot better if there was some indication that they truly wanted to be a member of the peace-loving nations of the world, the free world."

It was a point of view that became policy. In public, Reagan successfully promoted huge increases in military spending. In private, he often shared anti-Soviet jokes with his intimates. He was so suspicious of his adversaries that he passed up three opportunities to go to Moscow after the deaths of Soviet leaders.

Even those who shared the president's approach found him lacking in basic information about the Soviet Union. When trouble-shooter William P. Clark became Reagan's second national security affairs adviser early in 1982, he began showing the president movies about the Soviets and foreign-policy issues.

This cinematic assistance helped Reagan deal with generalities but did not fill in gaps on complex arms-control issues. On May 9, 1982, Reagan called for "dismantling the nuclear menace" in a speech at his alma mater, Eureka College, where he unveiled a major strategic nuclear arms reduction proposal, which he called "START" and which the Soviets quickly rejected as one-sided. Many months later, Reagan acknowledged that he was unaware that Soviet nuclear strategy relied most heavily on mammoth land-based intercontinental ballistic missiles, which would have been cut by three-fourths under START without comparable U.S. concessions.

Reagan's speeches reflected a dualistic view. On the one hand, he feared Soviet military prowess and considered the Soviets "the focus of evil" and the "evil empire," as he told the National Association of Evangelicals on March 8, 1983. He warned that audience not "to ignore the facts of history and the aggressive impulses of an evil empire, to simply call the arms race a giant misunderstanding and thereby remove yourself from the struggle between right and wrong . . . . "

But Reagan also believed that communism was a flawed system headed for the "dustbin of history," the fate that Karl Marx predicted for capitalism. In an address to the British Parliament on June 8, 1982, Reagan said denials of freedom and other restrictions had resulted in "the decay of the Soviet experiment."

In Reagan's view, expressed as early as 1980 in an interview with The Washington Post, the arms race had a potentially beneficial consequence if the burden strained the Soviet economy and pushed Moscow to the bargaining table. For Reagan, therefore, the summit seemed a natural consequence of the U.S. buildup.

"The president believes in the success of what he has done to restore America's defenses," a former senior adviser said. "This logically leads him to the conclusion that the Soviets might be willing to strike a bargain."

Political events, pressure from key advisers and diplomacy pushed Reagan in the same direction. The business of diplomats is diplomacy, and State Department professionals were uncomfortable with the absence of a U.S.-Soviet dialogue.

Reagan's first secretary of state, Alexander M. Haig Jr., had formidable anti-Soviet credentials. But the former NATO commander, under pressure from European allies, raised the possibility of renewed arms-control talks early in Reagan's first term. This pressure culminated in a proposal in November 1981 to eliminate all medium-range missiles in Europe, a plan unveiled in a dramatic international television speech timed for its European audience.

The speech reflected Reagan's discovery that political pressures, at home and abroad, did not leave him a free hand in dealing with the Soviets. After George P. Shultz replaced Haig in mid-1982, pressure for U.S.-Soviet dialogue increased sharply.

By mid-1983, White House officials were talking openly about the possibility of a summit meeting in the reelection year of 1984. Political advisers, reportedly including Nancy Reagan, had concluded that the president was potentially vulnerable on the "peace issue" unless he muted his anti-Soviet rhetoric and began to bargain. A more realistic START proposal was drafted. A series of external events delayed what one official called "the drift toward a summit." The most serious came on Sept. 1, 1983, when a Soviet fighter shot down a Korean Air Lines passenger jet, killing all 269 persons aboard.

On Oct. 17, 1983, Robert C. McFarlane replaced Clark, giving the administration a national security affairs adviser and secretary of state who shared the view that a summit was desirable. Soon afterward, Reagan told reporters that he would no longer refer to the Soviets as the "focus of evil."

The culmination of this effort was an unusually conciliatory televised speech on Jan. 16, 1984, in which Reagan said the superpowers faced "a year of opportunities for peace." More than any other event, the speech put Reagan firmly on the road to Geneva. After Soviet leader Konstantin Chernenko died last March 10, Reagan agreed almost casually to invite Gorbachev, his successor, to a summit.

Some U.S. officials say Reagan has traveled the road to the summit without altering his fundamental views. But one adviser offered a cautionary note, observing that the president referred to "so-called Communist China" only after he had visited the People's Republic of China in 1984.

"Reagan is not an intellectual in any sense, but he is powerfully influenced by his experiences and intuitively aware," this adviser said. "Personal experience counts with him, and this could be the most important trip of his presidency."