The main opposition Democratic United Party said it was sorry but grateful to independent Ahn Cheol-soo for his decision to drop out of the presidential race and support its candidate Moon Jae-in.

Minutes after Ahn’s announcement to quit, Moon said on his Twitter account, “I am deeply sorry to Ahn and his supporters.”

Moon’s campaign office said that with Ahn’s backing, the liberal opposition campaign would achieve a change of government that would usher in a “new politics and new era.”

“We are indebted very much to Ahn. We are sorry and grateful to him,” Moon’s spokesperson Jin Sung-joon told reporters.

His camp also said that Moon would have the time to express his “highest courtesy” to Ahn and would soon express his thoughts about being the liberal opposition’s unified candidate.

Over the last few weeks, Moon and Ahn had struggled to reach agreement on how to merge their candidacy. Opinion polls were cited as the most likely method but the candidates differed over how to select the survey participant.

Amid the tight race, the ruling Saenuri Party criticized their merger efforts as mere political engineering to retake power from the conservative bloc. Other critics argued that their delayed merger impeded proper pre-election activities, such as presidential debates.

Throughout the day Moon’s camp had been in a subdued mood with the failing talks fueling concerns about the coalition.

While the two sides had ultimately reopened communication channels, the DUP appeared ill at ease with the ultimatum.

Moon’s communications chief Rep. Woo Sang-ho of the DUP said that while the proposal from Ahn’s side was a compromise from its earlier position, the use of “ultimatums between partners would be difficult for the public to understand,” before the talks were resumed.

The mood had disintegrated further after the special envoys failed to reach an agreement with Rep. Jin Sung-joon, Moon’s campaign spokesman, saying that a direct discussion between the candidates was the only remaining hope for the coalition.

By Song Sang-ho and Choi He-suk 
(sshluck@heraldcorp.com)(cheesuk@heraldcor.com)