Ahn Cheol-soo, former leader of the People’s Party, is quickly rising as a strong presidential contender.

According to the Gallop Korea poll conducted from March 28-30, Ahn surged to second place. The second spot had been occupied by South Chungcheong Province Gov. An Hee-jung, who is competing in the primary of the Democratic Party of Korea.

Ahn gained 9 percentage points to 19 percent, almost doubling his support from a week earlier, An fell to 14 percent and Moon was unchanged with 31 percent.

He retook the No. 2 spot 10 months since he had last claimed the position in May 2016.

In a scenario of only Moon and Ahn contesting for the presidency, their gap was negligible, coming within the margin of error, with Moon and Ahn at 41.7 percent and 39.3 percent, respectively.

The primary reason for Ahn’s surge is that he has absorbed a large portion of supporters for An as he has failed to catch up with Moon in the primary race. In a scenario where An fails to win the nomination, 35 percent of his supporters turned to Ahn.

Ahn’s emergence is being driven by voters’ psychology to hold the distant front-runner in check. The number of voters who do not want to see competition on a lop-sided playing ground is fast increasing. They first saw the most likely challenger to Moon in An and are now turning to Ahn.

Moon has brought this situation upon himself. His camp has often been criticized for acting like a clique toward his primary rivals. His divisive and vindictive populism were worrisome.

His pledges on national security issues caused anxiety. He said the ongoing deployment of a US anti-missile system to fend off North Korean missile threat had not been ratified by the National Assembly so that he will seek the ratification of it if he takes power. He said he would visit North Korea first if elected president, reopen an industrial complex in North Korea and resume South Korean tourism of a North Korean mountain. The promises sound far removed from reality.

Ahn was quite different from Moon as to national security and the missile shield issue.

He clearly showed his conservative view of national security. He said in a recent TV debate that he would try to defend the country through tight security measures and a strong Army. He also said the first thing he will do if elected president would be to nominate the chief of the national security office.

But the problem is the People’s Party platform pursues a sunshine policy, which emphasizes inter-Korean economic cooperation.

Ahn has not reached agreement with the party over the Terminal High Altitude Area Defense anti-missile system. He first opposed the deployment of the system and later backed off, saying its deployment was an unavoidable choice. He demands the party change its platform against the system, but its leadership stick to a cautious tone.

If Ahn wants to see his rating keep rising, he needs to iron out his differences with the party over national security issues.

The presidential election is 36 days away. This week the list of presidential nominees will be finalized. Moon, Ahn, Hong Joon-pyo of the Liberty Korea Party, Yoo Seong-min of the Bareun Party and Sim Sang-jeung of the Justice Party are expected to compete for the presidency.

Ahn’s rise will be meaningful to anti-Moon voters if the race comes down to a one-to-one battle between them. He has shown the possibility of catching up with Moon in that scenario.

Kim Chong-in, a former interim chief of the Democratic Party of Korea, Chung Un-chan, a former prime minister, and Hong Seok-hyun, former chairman of JoongAng Media Network, got together last week to discuss an attempt for a coalition against Moon.

To gain support for an alliance against the front-runner, candidates should find common ground on crucial issues such as national security.

Before doing so, they need to narrow their differences, if any, with their party platforms. If they unite while neglecting such cracks, it will not be easy to unite voters.