Tactical voting (voto útil) means choosing a candidate or party other than your first preference in order to achieve a strategic outcome — for example, concentrating support to ensure a preferred candidate reaches a second-round runoff, or to prevent a disliked candidate from winning.

In Portugal, tactical voting is particularly relevant in presidential elections (where a two-round system is used) and in legislative elections (where proportional representation means small parties can lose votes to threshold effects in smaller districts).

Party leaders frequently urge tactical voting during campaigns, asking supporters of allied or similar parties to consolidate behind the strongest candidate to maximize seat counts or prevent rivals from gaining ground.