He criticized the policy of the mayor of Gdańsk, Paweł Adamowicz, and proposed, among others, abolition of parking fees in the Brzeźno district.

On April 26, 2018, PiS president Jarosław Kaczyński announced that Kacper Płażyński would be the party's candidate for the mayor of Gdańsk during the 2018 local elections.

[9] In the parliamentary elections in 2019, he ran for the Polish Lower House (Sejm) in the Gdańsk constituency from second place on the Law and Justice list.

[11] On October 24, 2019, Kazimierz Koralewski took over his duties as chairman of the Law and Justice councilors club in the City Council of Gdańsk.

[5][15] He is also the initiator of the establishment of the Social Committee "Gedania - STOP lawlessness in historic areas",[16] whose goal is to restore the historic areas of the Gedania sports club to the inhabitants of Gdańsk, as a place of sports and a symbol of Poles' activities in the Free City of Gdańsk.

As part of pro bono legal assistance, he defends the weaker, e.g. represents the residents of a tenement house sold together with its tenants to a private investor,[17] an unjustly dismissed employee of the Biedronka retail chain,[18] drivers in the so-called the parking scandal.