As of yesterday, the washer on my Kenmore stackable no longer spins for the spin cycle. It fills and drains fine, but will not spin at all. Previous wash loads had spun just fine. The lid switch seems to be fine because I can hear the relay click off and on if I try to lift then close the lid during the spin cycle. Any ideas what would cause this?

I bypassed the lid switch, left the lid open and opened the front panel, then started the spin cycle. I noticed the belt starting to move real slow, and put a screwdriver against the flat part of the pulley to see if it was spinning and found the pulley to be spinning much faster than the belt was moving. I pushed the drum a little to help start spinning and it began to spin great on its own. I also ohmed out the lid switch and it is working fine. It looks like I am going to need a new tight belt. It looks fairly easy to swap out, except for reaching the back side of the pulleys.