Do I have a bad ignition switch?

What comes across battery terminals when running? Did you do voltage drop on battery cables? Check ground contacts and voltage drop? What relay was tested? Starter? Main ECM relay? Did you replace battery or alternator first? Did old alternator ruin new battery?

You could have a bad ignition switch. Does dash lights stay on longer than they normally would after starting? This issue will drain battery quickly.

Thank you, but no, that wasn't a problem. At the moment there is no power into the cabin; no lights, nothing. Yesterday I replaced the alternator fuse, and verified that the ignition and starter fuses had continuity; they also looked intact with a visual. I have 12.7V at the starter solenoid, the negative cable grounds were tight. I checked both leads for the ignition switch, no voltage. I think I have narrowed it down to the battery cables, the ignition switch (I could have measured for voltage incorrectly), or, ouch, the fuse block circuit board. I have not verified ohms at the ground connections yet. But, that may take care of itself when I replace the battery cables. More thoughts?

Did you check any relays or power to the fuse block on these important relays and fuses relating to ignition. Also the main relay needs checked.

Check all grounds, alternator, engine and body grounds.

Checked ignition fuses, they were ok visually and had continuity with the ohm check. I have not checked the main relay. I will let you know. Thanks.

Starter and fuel relays also

Did you verify body ground? Maybe like a fusable link?

I appreciate the to-do list, as I was out of ideas. Thank you. I will let you know.

I replaced the battery cables, cleaned ground connections and it worked. Thank you.

Sounds awesome!!! Crazy how one wire can do so much. That deserves 2 thumbs up!!!!!

Thank you for that and the great questions and answers!