Lotteries in most states are okay for Non Profit groups, but Political groups? I think this is worthy of checking out.
U.S. Federal Gambling laws http://www.gambling-law-us.com/Federal-Laws/
In most states, non-profits need to obtain a license for gambling. The terms need to be spelled out an certain rules need to be followed.
Obama’s contest will have to be changed to include some way to enter at no cost (except to the soul).