Imagine a game of pretend where you and your friends want to make a king! You each get to choose someone you like for the job, and then you all have to try and convince the other players to pick your candidate too. If you manage to get enough support for your pick, then you win!
A "kingmaker scenario" is just like that game of pretend. It happens in real life when there are a number of people running for something important like president, governor, or even just the captain of the soccer team.
Sometimes no one gets enough votes to win outright, which means they don't have enough supporters to be in charge. But there might be one person who has a lot of power because they have a group of supporters who didn't pick the winner, but they have enough votes to create a majority if they support one of the losing candidates.
This person becomes the "kingmaker," because they get to decide who will become the winner! They have a lot of power and everyone will be watching to see what they decide to do. It's kind of like being a referee in a game: you get to decide who wins and who loses.
It can be very exciting and nerve-wracking in a kingmaker scenario because even though one person has the final say, everyone else is trying to persuade them to go their way. It's a big responsibility, but it's also a lot of fun to play!