Regardless of whether or not the election went your way:
How would you expect your child to behave at the end of a competition - sport, intellectual, or student government?
What is the appropriate protocol for winning?
What is the appropriate protocol for losing?
Do that - the children are watching.
Yes, I know this feels like the end of life as we know it. This makes our responses even more important.
We can agree to disagree.
Shake hands and get on with it. We're going to be spending lots of time together.
If you're on the winning team, don't gloat and rub it in.
If you're on the losing team, be gracious and allow the winners to enjoy their victory.
Now, everyone go to your room and think about your behavior.
Don't come out until you can play nice.