Democratic Party of Korea Chairperson Rep. Lee Jae-myung has come under fire after he was caught on a hot mic saying he “put on a show” after a campaign event Sunday.

“I put on a show of working (hard). My back hurts,” the main opposition leader said as he was getting into his van while still live on air on his YouTube channel.

The hot mic remarks came immediately after Lee held a campaign rally in a district in Incheon, where he is running for a second term in the National Assembly.

The clip of Lee’s remarks quickly went viral online, giving his rival People Power Party candidate, Won Hee-ryong, a chance to strike a blow. Won was the land and transport minister under President Yoon Suk Yeol before he stepped down to enter the National Assembly race.

“I would work wholeheartedly -- no show, no pretenses,” the former minister said in a Facebook post.

In the Incheon district, which has long been Democratic Party turf, Lee has been consistently leading in all published polls. Won is not far behind, with the latest polls indicating a gap of three to four percentage points.

The National Assembly election is on Wednesday.