The free healthcare policy turned out to be a major vote-winner for the party during the campaign.

vote-winner 是由名词 vote（投票）和 winner（获胜者）组成的复合名词。vote 指"选票、投票"，winner 指"获胜者、赢家"。 vote-winner 的字面意思是"赢得选票的人或事物"，引申为"能够吸引选民支持的政策或承诺"，即"票仓"或"拉票利器"。