SEOUL, OCT. 16 -- South Korea's presidential campaign kicks into high gear this weekend, with the four major candidates traveling to the provinces for rallies and opposition leader Kim Dae Jung saying "it is certain" he will run.

South Koreans hope that a presidential election set to take place in two months will bring the first peaceful transition of power in this nation's coup-blemished history.

Four candidates are vying to succeed President Chun Doo Hwan when he steps down in February.

To the delight of the ruling party, two of the four are rival opposition leaders Kim Young Sam and Kim Dae Jung, who have abandoned their pledges of unity and are training most of their fire on each other.

Kim Young Sam, president of the opposition Reunification Democratic Party, declared his candidacy last Saturday. Kim Dae Jung's announcement today in a television interview appeared to make final a split that had been growing since July and that many government opponents fear will ensure the election of the ruling party's candidate, Roh Tae Woo.

Kim Young Sam will travel to the southeastern port of Pusan in his home province Saturday for a rally that his aides predict will draw 2 million people and dwarf a similar homecoming parade that Kim Dae Jung staged last month.

Kim Dae Jung, who belongs to the same party, will hold a rally in Chongju at the same time.

"I think once again the opposition is helping us," said Hyun Hong Choo, spokesman of the ruling Democratic Justice Party.

Ruling party candidate Roh will address a youth gathering in the provincial capital of Taejon.

Taejon happens to be home territory for the fourth likely candidate, former prime minister Kim Jong Pil, who is considered likely to draw conservative voters away from Roh. He is to attend a rally Saturday in Chonan.

The unpredictable four-way contest appears to be almost the only subject of conversation these days for South Koreans, whose last opportunity to cast a meaningful vote in a presidential race came 16 years ago.

A similar campaign in 1980 was interrupted by a military coup staged by Chun, Roh and several other generals.

This time Roh, now a civilian with several ministerial posts on his resume, insists that there will be no military intervention.

He has been campaigning like a man who takes democracy seriously, inviting street sweepers and bus conductors to his home for dinner, holding hands with handicapped children and distributing color pamphlets that show him chatting with President Reagan during his recent visit to the White House.

The Democratic Justice Party, until recently synonymous with the government, also has been pressing government bureaucrats for some election-time help.

At times reluctantly, the government has agreed to higher rice payments to farmers, lower gasoline prices for consumers, a postponement of bus fare hikes until after the election and what the opposition calls a pork-barrel-bloated budget.

This week, for example, the government agreed to pay 14 percent more than last year for rice that it buys from farmers, although farmers' expenses have not increased much.

"I am well aware of the government policy to keep the inflation rate at a single digit figure," Roh said.

But, he added, "the administration has to take into account the enormous financial damage farmers suffered due to floods and typhoons this summer."

A fellow ruling party legislator put it more simply. "How can I ask for ballots from my constituents with a single-digit raise?" Rep. Ahn Byung Kyu asked.

The opposition party accused the Democratic Justice Party of going too far when it handed out gifts to voters during the recent celebration of Chusok, a harvest celebration.

But ruling party spokesman Lee Min Sup called Chusok gift-giving a "beautiful tradition" and noted that opposition legislators had distributed presents, too.

For the most part, though, the opposition's two Kims have been busy sniping at each other.