BRATISLAVA, Slovakia — During the final debate before Saturday’s presidential election in Slovakia, the men were arguing, but the only woman onstage, Zuzana Caputova, looked on calmly.

Stefan Harabin, the former justice minister and a champion of ethnic nationalism, accused Muslim migrants of “killing and raping European women in Germany and France” and claimed his opponents wanted to destroy Slovak culture.

But Ms. Caputova did not respond to the outrage. In a political climate where stridency is often rewarded and crudeness frequently seen as a marker of authenticity, she has clung to the belief that decency is what voters want most. And it seems to be working.

In an interview the morning after the debate, she said: “Even though people might not agree with all my opinions, they can build a bridge of trust to me because I act with civility. Even if I fight, I don’t fight the person, but only the actions of the person.”