Episode 3 of "I Am A Running Mate" unfolds 22 days prior to the elections, with Ji-hun and Se-hoon engaging in a heartfelt discussion about Ji-hun's choice to become Won-dae's vice presidential candidate. Despite Se-hoon's irritation, his friendship with Ji-hun remains unshaken, free from anger.
Later that day, Sang-hyeon extends an invitation to Se-hoon for his birthday bash. As night descends, a chauffeur deposits Se-hoon at Sang-hyeon's apartment, where he finds himself among a crowd largely unfamiliar to him, save for Mi-na and Jeong-hui. Sang-hyeon introduces Se-hoon and Jeong-hui to the gathering as his running mates, and the festivities commence.
The atmosphere is thick with the scent of alcohol, and Se-hoon too is offered a drink. He politely declines, to which Sang-hyeon stands in solidarity, citing his recent cram school escapades and the impossibility of returning home intoxicated. However, Ho-suk, one of Sang-hyeon's acquaintances, mutters under his breath that Se-hoon is a simpleton. Se-hoon, taking these words to heart, decides to down a mug of liquor in a bid to prove Ho-suk wrong.
Ho-suk, who harbors a dislike for Se-hoon, continues to bait him throughout the party, subtly insulting him at every turn. Se-hoon, fueled by anger, lunges towards Ho-suk, almost sparking a brawl, but Jae-won intervenes just in time.
The evening takes a turn as Se-hoon finds himself inebriated. When he awakens the following morning, Mi-na lies beside him in bed. Se-hoon has hazy recollections of Mi-na assisting him to his room the previous night but remains uncertain if their encounter extended beyond mere help.
At school, Se-hoon confides in Ji-hun about the party, extracting a solemn promise from him to keep the incident confidential. Unbeknownst to them, Gyeon-tae eavesdrops on their conversation from the shadows.
In the classroom, Sang-hyeon's campaign enjoys widespread support, with Hyun-jin lending a hand by crafting campaign posters. She unveils her creations to her classmates, who are thoroughly impressed. In gratitude, Hyun-jin invites the entire class for burgers after school, a proposal met with enthusiastic agreement. However, Gyeong-tae and Ui-jun decline, citing choir practice commitments.
Sang-hyeon's electoral journey commences with the valuable support of fellow students, particularly those belonging to Se-hoon's class. With the approval of their creative posters secured, Jae-won feigns illness to skip school and collects the freshly printed posters from the print shop. The students then enthusiastically plaster these posters across the school premises, later indulging in a cheerful meal of burgers and soda, where Se-hoon's spirits visibly soar. However, this uplifting scene does not sit well with his adversaries.
Later that day, Jong-su and his gang of bullies corner Se-hoon in a dimly lit room within the school. They taunt him relentlessly, reminding him of his perceived insignificance. They issue a chilling warning, urging him to contemplate his school life post the seniors' departure, vowing to continue their torment even into their own senior year.
On his way back home, Jae-won perceives Se-hoon's subdued demeanor. Upon noticing bruises on Se-hoon's neck, Jae-won realizes that he has been the victim of bullying. Jae-won gently reminds him of his ongoing vice-presidential campaign and urges him not to let the bullies dim his spirit.
Elsewhere, Won-dae and his campaign team find Sang-hyeon's posters adorning every corner of the school. It becomes evident that Sang-hyeon has beaten the official campaign start date. However, Won-dae remains unruffled, strictly instructing his team to adhere to the campaign protocols established by the school authorities. As the incumbent vice president and a veteran of electoral battles, Won-dae exudes confidence, believing that he holds a distinct advantage.
Sixteen days prior to the elections, the morning light saw the arrival of the police at the school gates. Won-dae was taken away for interrogation, leaving everyone puzzled as to the reason behind the police's unexpected visit for him. Later that evening, after wrapping up his choir meeting, Ji-hun insisted that Se-hoon accompany him for a meal, his tone filled with determination. However, just as plans were being made, Sang-hyeon interrupted with an invitation for Se-hoon to join the team at his family's hotel for a photoshoot and further campaign strategy sessions.
Caught between commitments, Se-hoon managed to squeeze in a call to Ji-hun during a brief lull in his schedule. Peering through the window, he spotted Ji-hun sitting in a restaurant directly opposite Sang-hyeon’s location, adorned with a birthday cap. The realization dawned on Se-hoon that Ji-hun's insistence on dining together stemmed from it being his special day.
Duty called Ji-hun away to join his classmates for the birthday cake, abbreviating their conversation abruptly. Se-hoon, standing sadly by the riverbank, watched as Ji-hun celebrated his birthday amidst laughter and camaraderie with his fellow students. Meanwhile, he was summoned back to resume the campaign meeting, his heart lingering by the festive scene across the water.
Twelve days prior to the elections, Jong-su and his rowdy companions joined Sang-hyeon's campaign, serving as its security detail. This decision came on the heels of a meeting they had with Jae-won, where they were accused of harassing Se-hoon. Subsequently, Se-hoon and Jeong-hui convened with Sang-hyeon to deliberate on the campaign promises. Jeong-hui had painstakingly conducted extensive research, emailing over a hundred schools to procure the pledges that had propelled last year's victorious campaigns. Sang-hyeon admired Jeong-hui's unwavering commitment, deciding that she should collaborate with him on shaping their pledges while Se-hoon was tasked with scouting locations for campaign banners.
However, Se-hoon found himself feeling marginalized within the campaign, believing that everyone else was contributing more professionally than he. Hyun-jin's poster designs outshone his, leading the team to approve hers while mocking his efforts. At school later, the news broke that a notorious voice phishing scammer had been apprehended. Coincidentally, Won-dae had encountered this individual shortly after the scammer had crashed his truck while driving under the influence. The police had detained Won-dae merely to present him with the Brave Citizen Award, which was given in recognition of his encounter.
This incident catapulted Won-dae to greater fame within the school, inadvertently impacting Sang-hyeon's campaign. Sang-hyeon and Se-hoon were disheartened to realize that their concerns had been unfounded. Se-hoon harbored feelings of envy, wishing that it had been Won-dae who faced arrest for losing his temper rather than gaining accolades.
