Krúpa ran as a candidate for OĽaNO in the 2020 parliamentary elections.[1] However, he was not a member of the party.[4] In the Parliament, he was the chairman of the National Assembly Committee for Defence and Security, a member of the Special Control Committee of the National Assembly to control the activities of the Military Intelligence and a member of the Permanent Delegation of the National Assembly of the Slovak Republic to the NATO Parliamentary Assembly.[1]
At the end of June 2022, Krúpa abstained from voting on the 1 billion Euro package for families proposed by Finance Minister Igor Matovič (OĽaNO), thus failing to support the override of President Zuzana Čaputová's veto.[5] Krúpa was the only OĽaNO MP to abstain, which brought him to the attention of SaS chairman Richard Sulík.[6]
On 28 July 2022, Krúpa announced his resignation from the OĽaNO parliamentary club. A day later he announced his move to the SaS club. About his transition he said: "I ran as a candidate for the anti-corruption movement and found myself in an ultra-conservative movement that fights against liberalism".[6] "He described as a red line the consideration of admitting the possibility of forming a minority government with the support of "various criminals, extremists and fascists" during the coalition crisis".[7] The Republican Council of SaS approved Krúpa as a team leader for defence, but Krúpa has not yet joined the party.[6]