Sunnis, Shiites Protest Iraq Constitution

I swear if this crazy idea of invading a Muslim country that as 3 separate ideologies, creating a single constitution and having it blossom into a strong democracy actually works... ANYTHING is possible... If it works back, history is going to look back and say "How the f%&k did America pull that off"?

What happens if in October, when the constitution goes before the people of Iraq for a vote, it gets voted down? What does the provisional constitution say about that?