Get out the vote

Get out the vote means reminding people to vote in an election. When a grown-up wants to vote to choose their leader or make a decision, they have to go to a special place called a "polling station." But sometimes they forget to go and vote or they might think that their vote doesn't matter. So some other grown-ups remind everyone to vote so that lots of people show up to the polling station and use their votes. This is because when many people vote, it makes the election fair and reflects the choices of all the people. So, "get out the vote" means reminding everyone to vote, so their voice and opinion is heard.