I also am not to bothered if people choose to smack their child, but I don't think it is necessary to get them to do what you want either. I think that if you don't do it to other children when babysitting, why do you need to do it to your own child??

I think a loud "stop" or, "that's it, in your room" and leaving them in their bedroom for 5 - 10 minutes so everyone can calm down will have the same effect.

I also don't believe in explaining everything to children either. IMO, the "you make me feel" statements were never created for dicussions with small children. That is professionals helping adults learn how to communicate effectively with other adults. I think you keep your instructions simple with kids and too much langauge (especially when they are overwhelmed) is too confusing.
I also like the 123 Magic strategy - which can be used with children about 2 +

anyway - back to your question - I think I'm lucky DH has never smacked his daughter, and we both agree - that while we wouldn't beat ourselves up over it if it happened, it's not necessary to get kids to do what you want. And I prefer to SHOW my child the appropriate way to act as well as teach them.

having said that... although I have lots of expereince with kids, have been in DSD's life since she was 4, and my mum had a baby when I was 18 (and I lived at home for most of the first 10 years of his life), I don't actually know how I will respond to my own toddler. But I hope I don't, cause... although it never hurt me.... I was afraid of my dad at times (and I had a perfectly normal upbringing!), and don't want my kids to ever be afraid of making a mistake and owning up to it with me.

we don't have control over each other, only our own reactions to things. All you can do is explain your perspective to DH, and if he chooses to smack, then really you can't do anything about it - cause that is his relationship with DD he is working on, and DD needs to know that whether you agree with dad or not, you will support his decision - it's a tough one!! I think I'm lucky that we agree on parenting style for the most part.

truly though... whatever either of you do - she will surely be fine ;-)