You may not need to go all the way up to the light itself. Would it be shorter to run a wire from the Switch for the light (I'm assuming that you have a switch near the door for the porch light)? You might be able to follow the hot wire that runs to the Switch.
If your porch light switch is on a panel with several other things (power awning, ceiling lights, etc.) you might also be able to run from that down to the area of the step.
2013 Rockwood 8289WS
Mods: Central Vac, PI EMS-HW50C, 2025RV, (2) SCS225 Trojans, PD9260, Awning Remotes & LED Lights, Eliminators, External Water Filter,, Intellijacks
2008 RAM 3500 Cab&Chassis Hauler Bed, B&W Companion Hitch
All My Modifications are at this link: