Episode 5 of "I Am A Running Mate" unfolds five days prior to the elections, with Sang-hyeon's team igniting their campaign rally with fervent energy. The entire school buzzes with chatter about Se-hoon's unfortunate accident, casting a shadow of suspicion. Gyeong-tae speculates that the mishap was orchestrated to elicit sympathy votes for Se-hoon, a notion Ui-jun firmly refutes, cautioning Gyeong-tae against spreading unverified rumors.
Sang-hyeon's team capitalizes on the rally's momentum, displaying a heightened sense of preparation and enthusiasm that electrifies the crowd. Conversely, when Won-dae's team ascends the stage, they captivate the audience with a skit depicting one of their pledges: establishing an umbrella rental service within the school for rainy days. Yu-gyeong and Ji-hun's shared performance in this skit stirs a wave of anger in Se-hoon.
The blue team, led by Sang-hyeon, is taken aback by the red team's (Won-dae's) innovative efforts. Despite this, Sang-hyeon's popularity surges to 47%, while Won-dae's slips to 52%.
Later, Tae-oh confides in Se-hoon, unraveling his significant discoveries. Earlier, Tae-oh had ventured to the music room to voice his grievances about using singing abilities to evaluate their exams, believing it unfairly disadvantages certain students. As he awaits the teacher's attention, amidst her conversation with another student, his eyes fall upon a note lying on her desk. It enumerates the top performers in their class, accompanied by annotations detailing their suitability—or lack thereof—as candidates.
Se-hoon's entry strikes a chord; it brands him as an unsuitable candidate due to his tarnished reputation, yet acknowledges his potential as a powerful tool to garner sympathy votes. To Tae-oh's astonishment, he catches Won-dae slipping the note, along with his notebook, into his possession, revealing Won-dae as the author of these insights. This revelation fuels Se-hoon's anger towards Won-dae, intensifying an already tense rivalry.
Sang-hyeon and Se-hoon find themselves amidst the hustle and bustle of Won-dae's campaign, eager to participate in an interview. Their footsteps eventually lead them to the election office, where they witness Gyeong-tae busy with an assortment of posters depicting Won-dae, destined for the media spotlight the following day.
Anger flickers across Sang-hyeon's face, fueled by Joon-Gyu's oversight in not informing him of the impending media interviews. He suspects Won-dae of employing underhanded tactics, leveraging his Brave Citizen award to sway the media in his favor. Joon-Gyu, however, remains unconvinced, insisting that Won-dae's actions fall well within the realm of legitimate electoral strategies.
Se-hoon endeavors to soothe Sang-hyeon's ruffled feathers, but his efforts only serve to fan the flames of the latter's irritation. Sang-hyeon's frustration boils over, lambasting Se-hoon for his perceived passivity in contributing to the campaign. He scoffs at Se-hoon's role, reducing it to mere spectating, commenting, and cheering for their friend Ji-hun. In a fit of impatience, Sang-hyeon snaps at Se-hoon to cease empty words and take tangible action.
That very night, driven by an insatiable urge to rectify the situation, Se-hoon creeps into the election office under the cloak of darkness, his hands wreaking havoc on Won-dae's posters.
The following morning, Joon-Gyu's voice crackles through the phone lines, alerting both the red and blue teams to the defaced posters. Gyeong-tae, desperate to shift the blame, attempts to implicate the blue team. But Se-hoon, his patience worn thin, strikes back. He accuses the red team of orchestrating the entire scenario to frame the blue team, echoing Gyeong-tae's earlier propaganda that claimed Se-hoon's accident was a charity vote scam. Joon-gyu, cautious of escalating tensions, cautions both teams to maintain a low profile while the matter is investigated.
After the meeting adjourns, Won-dae pulls Gyeong-tae aside, disciplining him for displaying disrespect towards his seniors in front of a teacher. His tone is stern as he warns Gyeong-tae to mend his ways and refrain from actions that tarnish the red team's reputation.
After their posters were vandalized, the Red Team staged a solemn silent protest during the third rally, holding up signs demanding that the school launch an investigation and mete out punishment to the culprits. Meanwhile, the Blue Team persisted in their campaign of lavish promises, vowing to gift each student a smartwatch should they triumph in the elections. By the rally's conclusion, the Blue Team's popularity had plummeted to 41%, while the Red Team's stood at 47%, with an alarming 11% of students opting to boycott the elections altogether.
The subsequent day, Gyeong-tae published a confession implicating Se-hoon in the lewd drawing of Yu-gyeon. Se-hoon, incensed, prepared to confront Gyeong-tae head-on, but Jae-won intervened on Sang-hyeon's behalf, thwarting his plans. Yu-gyeong confronted Gyeong-tae for resurfacing the issue and embarrassing her once more. Gyeong-tae defiantly responded that he would stop at nothing to sabotage Se-hoon for Won-dae's sake, labeling him a traitor. Later, Gyeong-tae met with Won-dae, who commended his actions. Won-dae dismissed Ji-hun and Yu-gyeong as mere backups, emphasizing that Gyeong-tae, akin to his shadow, held greater significance.
As the episode drew to a close, Se-hoon, seething with rage to the point of near suffocation, summoned Jong-su to meet him in the bathroom. In a fit of fury, Se-hoon berated Jong-su, instructing him to do whatever it took to silence Gyeong-tae, hinting at drastic measures such as assaulting him with a motorcycle or even killing him.
