I was able to accomplish this using separate {if} statements. The only hangup I ran into was when you click one of the alternate options it must be clicked twice to activate the toggle.
{formtoggle: name=one; default=yes}1 Potato{endformtoggle}
{formtoggle: name=two; default=no}2 Potatoes{endformtoggle}
{formtoggle: name=three; default=no}3 Potatoes{endformtoggle}
{if: two==yes}{one=no}{three=no}{endif}
{if: one==yes}{two=no}{three=no}{endif}
{if: three==yes}{one=no}{two=no}{endif}