People Power Party candidate Yoon Suk-yeol (left) and People's Party candidate Ahn Cheol-soo (Yonhap)

The campaigns of main opposition presidential candidate Yoon Suk-yeol and minor candidate Ahn Cheol-soo clashed Monday over the right way to merge their campaigns, with Yoon's side rejecting Ahn's proposal of a public opinion survey.

Ahn of the centrist People's Party proposed the merger with Yoon of the conservative People Power Party (PPP) on Sunday, with less than a month to go until the March 9 election.

Ahn said the two sides should field a single candidate to take on ruling Democratic Party (DP) presidential candidate Lee Jae-myung and suggested they choose between him and Yoon through a public opinion survey similar to one used to determine the opposition standard-bearer during last April's Seoul mayoral by-election.

Yoon and his party welcomed the idea of a merger, which has long been considered a potential game-changer in a remarkably tight presidential race.

But they balked at the notion of a survey over concern some of the respondents, who are supporters of Lee and his party, could pick Ahn just to increase Lee's chances of winning the election, as polls show Lee and Yoon neck and neck at around 40 percent support each but Ahn a distant third at below 10 percent.

Ahn's campaign has argued its candidate is just as likely to suffer from such distortions because some polls show he would beat Lee by a larger margin than Yoon in the hypothetical scenario of an opposition merger.

Moreover, Ahn's campaign has noted the proposed survey was approved by the PPP ahead of the mayoral election and resulted in Ahn losing the unified opposition candidacy to then PPP candidate and now Seoul Mayor Oh Se-hoon.

"If they're worried they can't beat Ahn (in a survey), how do they plan to beat Lee?" Lee Shin-bom, a co-chair of Ahn's campaign, said during a campaign committee meeting Monday.

During a meeting of Yoon's campaign committee, campaign chief Rep. Kwon Young-se called for a "big-minded unification," apparently pressuring Ahn to drop out of the race and throw his weight behind the PPP candidate's campaign.

"That's because both the No. 1 and No. 2 calling of the era and command of the people is regime change," he said.

Kwon also asked that Ahn "consider what would be the surest and correct way to achieve regime change."

When asked by reporters whether Yoon plans to meet with Ahn to discuss their merger, Kwon said he had nothing to share.

Speculation of a possible meeting between the two has grown since Yoon said a merger, if it were to happen, would result from a one-on-one meeting, such as "over a cup of coffee," and not through drawn-out negotiations between their campaigns.

A PPP official told Yonhap News Agency the party is weighing different incentives for Ahn to back Yoon's campaign.

"Offering the position of prime minister or several ministerial positions will only end up insulting Ahn," the official said. "We'll approach him with sincerity from the perspective of values rather than political engineering."

The ruling DP downplayed the merger talk amid concern it could steal the spotlight from Lee's campaign.

"I feel (Ahn's proposal) was effectively a (way of putting up a) barrier against a merger," Rep. Woo Sang-ho, chief of the DP campaign committee, said in a TBS radio interview Monday.

"I don't think the chances of a deal are high." (Yonhap)