Thanks, Lee, yes, the clutch switch connector is a pain to get to. I just found it.
The more I think about this, the more I think the advice to check the battery condition is the most important first step. A low battery will still light everything up, but won't turn over.
The ride home is somewhat telling. What are the chances the clutch switch worked when you left the yard, but not when you got home? Pretty low. But a battery subjected to a few weeks in the cold weather you've been having out there ... easy to believe that might have just enough juice to start, but not enough to restart if not charged for a while. And if the battery's a few years old by now, that might be enough to tip it over the edge to being unrecoverable.