This is the vexing question of the "serial comma."

I, personally, believe in the serial comma. Its lack leads to such amazing sentences as "I dedicate this book to my parents, Ayn Rand and God."

In practical terms, choose either to use the serial comma or not to use it, then be consistent. Half of your readers will be convinced that you're wrong, no matter which you choose.

This is a better URL: http://members.aol.com/MorelandC/HaveOriginsIndex.htm

The phrase refers to the finish line in a horse race, a string streched across the track. A very close race is uncertain "down to the wire," that is, to the end.