The popularity of televised political debates is growing, attracting millions of viewers. However, evidence that such debates can shift voters’ attitudes is mixed and the impact on voters’ preference is also mixed. In addition, the evidence comes mostly from presidential elections in the United States and almost exclusively from established democracies. A call for comparative research in new democracies has been made several times. Our research answers the call and contributes to this debate by comparing two experimental studies based on first-order national elections and second-order European Parliament elections in Slovakia. To our knowledge, this is the first time such a study has been performed in a post-communist EU country. We employed a pre-test/post-test experimental design in a controlled environment with participants randomly assigned to both groups. The results show that debate exposure has a stronger effect on opinions about candidates’ leadership skills, credibility, and economic competence if the candidates were previously unknown. Familiarity with the candidates and pre-existing preferences also function as a block to preference change. Almost all of our findings are in line with previous research originating from Western contexts. Therefore, we conclude that the causal mechanism linking debate exposure to voters’ preference and attitudes in the post-communist context is similar to that in Western countries with long-term democratic traditions.