I have a Kenmore washer model # 20722991. During spin cycle regardless of the amount of laundry in the tub it vibrates. Vibration is strong enough that the machine dances on the floor. I have tried distributing loads evenly, but that does not help. I ran it in spin cycle empty, but it still vibrates.

Need help.

Sounds like one of the tub snubbers or support springs have come loose. When that happens they will dance around pretty good.

Sounds like one of the tub snubbers or support springs have come loose. When that happens they will dance around pretty good.
How can I fix this problem?

First you are going to have to take the service panel off the machine and have a look inside to discover exactly which part is causing the problem. Once you find it then get a replacement and install it. You have to have the skill level to be able to do this.