2001 V6 Dakota not starting

My 2001 V6 Dakota isn't starting. I checked the spark plug and fuel pump and they seem to be fine. The engine is spinning but it won't turn over. I turned the key once and it started up but as soon as I let go of the key, the engine shut off and it won't turn back on, it just cranks. I charged the battery for about 15 minutes even though the gauge didn't show that it was low. Still didn't work. Does anybody have any idea what else I should check or do before I take it in? (oh yeah, and yes it has gas, I've been asked that too many times) Appreciate any responses.

"The engine is spinning but it won't turn over"

The first time the cat clogged on my truck, it would crank for days, but it wouldn't fire up. That's what happens when your exhaust clogs. Change your cat.

I know that's my solution to everything...

Do you have to pump the gas to keep it started?

Just letting people know, in case this happens to them. Evidently I had a blown fuse but it wasn't an ignition fuse. A friend of mine told me to check that. The fuse was for the fan. But since it was blown it couldn't complete the circuit and therefore could not start. Amazing how something small like that can ruin the whole operation.