What would cause a fuse to continually pop for tail lights for 2001 buick regal?

Fuse pop's for the tail lights and some other dash light have gone out. The fuse box that houses this particular fuse is under the hood but I don't know if I have a short somewhere.What would cause a fuse to continually pop for tail lights for 2001 buick regal?more than likely a bad earth somewhere, or a surge in the current caused by a dodgy altenator...

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