Replaced the spark plug -- still same result and as far as I can tell there is no oil in the chamber. Also checked the oil level and, while it's at the very top of the fill line on the dipstick, it doesn't look to me to be so full that it would cause problems (especially given that I've already run it 5-6 times with no issues).
Do I need to re-gap the spark plug? I bought it from an auto parts store and it looks like the gap is a little wider than on the old plug I removed.
Next up I will confirm that I have a spark to the plug. I'll also drain a little oil (just to be safe) and also drain/replace the fuel.
Thank you.
-Erik