The purpose of this action research is to introduce a debate activity contextualized in a scientific topic and explore its effectiveness in prompting teacher candidates' (TC) argumentation skills and affective perception of argumentation. We also investigate the separate impacts of the different aspects of the debate activity. Through comparing the quality of structural argumentation from 28 elementary TCs before and after the activity, we find that the debate has enhanced the TCs' argumentation skills in terms of the use of rebuttals. The transcript data further reveals that the confrontational aspect of the debate, i.e. Clash and Extension, are most effective in arousing high-level arguments as well as most risky in triggering negative TC attitudes towards argumentation. Through reflecting on our action of implementing the debate, we suggest a revised rubric for argumentation assessment in which sophisticated argumentation skills are epitomized by not only rebutting but also synthesizing various information and multiple perspectives to reach a conclusion.