First of all if a con man is really good, you most likely won't spot him/her. At least millions and millions of voters can't. 
Second, if someone is vague in a business talk when it's time to be clear about details, that's suspicious.
Third, people rarely, very rarely do something without seeking for their own profit. If something contradicts common sense, there probably is some skeleton in the closet.

Second, if someone is vague in a business talk when it's time to be clear about details, that's suspicious.
Third, people rarely, very rarely do something without seeking for their own profit. If something contradicts common sense, there probably is some skeleton in the closet.