SEOUL, DEC. 19 -- Ruling party candidate Roh Tae Woo stood before a massive crowd in central Seoul one week ago and, as his bodyguards lobbed tear gas grenades at protesters, promised the nation "harmony and unity" if elected.

Four days later, South Koreans offered Roh a chance to make good on that promise, electing him in the nation's first genuine balloting in 16 years. On Feb. 25, Roh is scheduled to become the first president to take power here without benefit of a military coup, an assassination or a student revolt.

Roh's chances of managing that peaceful transition improved with his surprisingly large margin of victory over his opposition party rivals, his backers believe. Protests against the election of the former general have, so far, been smaller than the ruling party had feared and have generated little apparent popular support.

But Roh's pledge of "national reconciliation" will not be quickly or easily achieved in a nation where political divisions are so deep, historically rooted and personally felt.

With Roh having won only a 36.6 percent plurality, with his two main rivals declaring his election fraudulent and invalid and with one region of the country solidly and bitterly against him, Roh is a long way from delivering harmony and putting tear gas permanently behind him.

"There are deep wounds, and they will take time to heal," said a senior government adviser. "I don't think anybody should expect a quick recovery."

In the short term, Roh's challenge is to ride out a wave of student protests and opposition cries of foul without cracking down so hard that he alienates the middle class, which so far seems inclined to accept his victory. He must accomplish this from the ambiguous position of president-elect, while President Chun Doo Hwan, with his hard-line instincts, remains officially in charge.

In the longer run, supporters and opponents here said, Roh must make good on his campaign promise to shed his military heritage and "repudiate any authoritarian attitude toward the people." Many Koreans who voted against Roh doubt his commitment to do so; others question whether Roh will have the ability to curb the powerful military and internal security bureaucracies that have enjoyed an almost free hand for decades.

"Perhaps he would like to move away from that, but how successful he will be is the question," said a former senior foreign service officer. "The bulk of his support, overt and covert, came from this massive bureaucracy, and his power base is a continuation of the present regime."

Supporters said Roh is determined to reform the government. In announcing his plan today to hold National Assembly elections Feb. 10, Roh indicated he wants to field a slate with 40 percent to 50 percent newcomers, replacing dozens of incumbents.

Roh also has shown a sensitivity to questions of style that differentiate him from the more imperious Chun and that are watched closely by many Koreans. Today he rejected a bulletproof Cadillac offered by the government after his victory. He will stick to his smaller, Korean-made car, and he chided his staff for stopping traffic for his motorcade.

"He's different than Chun," said Kim Song Hee, 21, an English literature major who supported the opposition. "I firmly believe he will do less militaristic things, more democratic things."

Still, the distance South Korea has yet to travel to heal its national divisions was evident this week in a shabby campaign office of defeated opposition leader Kim Dae Jung in a working-class district of Seoul. Unwashed teacups and tattered posters signaled the failure of Kim's campaign, but a few workers still huddled around the kerosene stove in the center of the room.

The workers said they knew, without doubt, that the police would soon raid their office and arrest them and that police already had killed demonstrators in Kwangju, capital of Kim's home province to the south. The Kwangju rumor, at least, was false, but the workers' siege mentality was very real, fueled by a conviction that both Korean and foreign media were concealing the truth of Roh's massive vote fraud.

To opposition candidates Kim Dae Jung and Kim Young Sam, who have refused to concede defeat, Roh is a military dictator, branded forever by his part in Chun's coup eight years ago and his close ties to Chun's authoritarian rule. To the ruling party, the Kims are dangerous demagogues, alleging electoral fraud without evidence to make excuses for their squabbling and defeat.

So to "ungrudgingly" concede, as Chun suggested, would be immoral in the minds of many opposition supporters. That is especially true in Kwangju, which showed itself to be almost a separate nation when it cast 94 percent of its votes for Kim Dae Jung, who received 27 percent nationwide.

"The discrimination against this region is centuries old, and during the past several years the sense of discrimination got aggravated," a ruling party official said. "This election aggravated feelings even more. It will take years, surely."

Roh promised during the campaign to heal the regional wounds. He said he would try to improve relations with China, in part so that South Korea's west coast ports could catch up to the bustling east, which faces Japan.

But when Roh visited the Kwangju area during his campaign he was pelted with eggs and rocks, and this week it has been the site of the largest protests against him.

Throughout the nation, in fact, there was little sense of celebration at Roh's election. Many of his supporters expressed relief, having feared a time of chaos if the opposition won, and many of those who voted against him expressed resigned acceptance. But there was no sense of excitement, of the opening of a new era, to propel Roh through his first 100 days.

Nonetheless, Wednesday's election showed that the conservative "silent minority" is larger than many analysts predicted, with almost 45 percent of the electorate choosing Roh or conservative former prime minister Kim Jong Pil. Many of those voters felt a stake in South Korea's growing economy, and their desire for stability will continue to be a force on Roh's side.

The Olympics, scheduled for Seoul in September, also help Roh, since most Koreans view it as a point of pride to host the games successfully. Even before the election, many analysts said any winner would be given a seven-month, Olympics-inspired grace period to prove himself and ensconce his regime.

The nation's robust economy is on Roh's side, too, as he prepares to handle labor strife expected in the spring. Economists are predicting 8 percent growth next year.

Finally, the disarray of the opposition, which allowed Roh to be elected, continues to help him now. While both opposition Kims demand that Roh step aside, they remain bitter rivals, unwilling to plan a common strategy. Kim Young Sam refused today to see an emissary sent by Kim Dae Jung.

Roh's plan to hold National Assembly elections soon may draw the opposition back into the political process as legislators start worrying about their jobs.