Sometimes, it seems obvious who is going to win an election. Even in that kind of election, it’s still important to vote.
Your vote matters, even when your candidate loses. Voting sends a powerful message to politicians. Every vote against a politician tells them that some people dislike their policies, and that it is costing them votes. Politicians care about everything that costs them votes, because their jobs depend on continuing to win elections.
It matters who wins elections. It also matters how much they win by. The closer an election is, the more the winning politician has to care what the opposition thinks. Even in a state where one party is almost certainly going to win, there’s a big different between getting 90% of the votes and getting 40% of the votes.
When you vote against a politician, you’re sending a powerful message. It makes everything else you do more effective. It means they’re more likely to listen when you and others call them. It means they’re more likely to feel that they have to show up at town halls, and more likely to take what you say seriously. Voting creates leverage in ways that matter, even when you lose.
This is also true when your candidate is almost certainly going to win. Vote anyway, because it matters how much they win by — every vote they get gives them more power to enact their agenda. When they win by more votes, they don’t have to be as worried about the opposition.
(And in any case, it’s inadvisable to get complacent. Sometimes elections are much closer than they seem.)
Your vote matters, even if your candidate loses. Your vote matters, even when your candidate is almost certainly going to win. It’s important to go vote when you’re eligible, even if it’s unlikely to change the results. Even when voting doesn’t change the outcome of the election, it does change the political facts on the ground.
Tl;dr Vote when you can, even in elections that aren’t close. It puts pressure on politicians in ways that matter. Whether or not your vote affects which politician wins, it will affect what the winning politician does.