Let me ask you this, do you really think you have to spank your child? Or do you feel that your voice and presence would be enough for them to understand you?
Not to derail the thread but I have come to agree with this as I've gotten older. People who beat their children, beat their children just as much as people who discipline by scolding/time out use scoldings and time outs etc. which means you can use the non violent approach and get the same results (or lack of). Think about it, there is really no act a 2 year old can commit that deserves a physical beating unless you failed to discipline at all the first 2 years. I was spanked as a child and believed I would spank my children for discipline. As a matter of fact, I laughed at the people who used time outs and firm talks, but my mindset changed and I don't think I am well behaved now because I was spanked. You learn right from wrong by being taught and those teachings being firmly reinforced when you stray.
Spanking is a behavior acquired through slavery. The only physical action I have taken against my daughter is a hand pluck. The rest is being firm, reinforcing good behavior and staying involved in what she is doing.
I'm not telling anybody what to do in their homes, but do you really think your level of discipline is a result of physical spankings? And were you ever spanked repeatedly for committing the same bad act over and over?