You swore that you'd be home by midnight you're never home by midnight
I left the porch light on, I left the gate unlatched
We both knew what we owed and neither one would ask
→ one of us was waiting, that's the whole first verse
CHORUS:
So keep the porch light burning low
So keep it lit till morning when the dark gets 'round you heavy
I'll be right here waiting up for you where you left me
With the porch light low and the gate unlatched
The shift from “waiting up” to “where you left me” gave the whole song its spine. That's the line the record hangs on.