The main opposition party’s front-runner Moon Jae-in is stepping up his attack against major initiatives of the President Park Geun-hye government, but his assertive stance has unnerved moderate groups within opposition parties.

In a series of remarks following Park’s impeachment -- who now awaits her impeachment trial at the Constitutional Court -- Moon laid out his vision for a “complete overhaul” of the nation and vowed to pursue “revolution” if the court decides to reinstate the president.

While energizing his liberal supporters amid mounting anger over Park and her governing Saenuri Party, Moon’s strong rhetoric has drawn criticism that it would ostracize moderate voters during the 2017 presidential election, which could take place earlier than expected if the president is ousted.

“No matter how outrageous we are, we have to find a solution to protect the people’s lives and property by observing the Constitution,” said South Chungcheong Gov. Ahn Hee-jung, an opposition heavyweight competing with Moon for the presidential race.

Since the National Assembly impeached the president over her connection to an influence-peddling scandal tied to her longtime friend Choi Soon-sil, Moon has rolled out a series of plans to overhaul the nation’s power structure, economic system and security policies. 

Describing the massive public protests against the president as an opportunity to “overhaul” the government system, Moon has pledged to eradicate the nation’s widespread corruption and wrongdoings among the political and business elites. 

In order for that to happen, Moon noted that removal of Park from her office is crucial and must take place promptly. He even suggested that the people should consider overthrowing the government if the Constitutional Court decides to bring Park back to power.

“Though it is hard to imagine, I think we are left with no choice but to pursue revolution,” said Moon in a media interview last Friday with Kim Yong-ok, a prominent liberal-leaning scholar known by his penname “Dohol.” 

Moon also demanded a shift in the president’s approaches on North Korea and diplomatic issues. He urged the government to shift away from its hawkish stance on Pyeongyang and pursue changes in bilateral military agreements with the US and Japan.

Moon has not always adopted such an assertive tone. His demands became stronger after the lawmakers passed the impeachment motion against Park earlier this month.

Compared to other liberal heavyweights such as Seongnam Mayor Lee Jae-myeong, who had called for the immediate resignation of Park, Moon distanced himself from such a proposal and suggested instead that Park should let the prime minister govern the nation.

Some Saenuri lawmakers criticized Moon for shifting his stance. They argued that Moon had become more assertive just to appeal to liberal supporters, who have been attracted to outspoken liberal politicians such as Lee since the outbreak of the Choi scandal.

“Moon should stop thinking about Lee. He should put the people first,” former Saenuri Floor Leader Rep. Won Yu-chul said on Facebook on Sunday. “His radical remarks violate the principles of democracy and the rule of law.”

By Yeo Jun-suk (jasonyeo@heraldcorp.com)