This is one of the most touchiest subject you can bring up in politics because the vote is the "power" of the whole country.
So the constitution what does it say about this. To do this we have to understand what it means to vote. To vote is to give you share to a certain side, and the side with the most shares wins. Then who has shares? The constitution itself (excluding the amendments) specifically says that only male land owners that were 18 could vote. But what for, surprisingly its not president, its not a senator but for representatives, governors, and state congresses. But otherwise that's about it. Now some people might say that's not right when it comes to who can vote I believe the age is right but the race thing no I believe every race should have the right to vote. But when it comes to what to vote for I believe that the founding fathers had the following in mind. If I could give you something for free...such as health care or food stamps you would probably vote for me too. But if you don't vote for me directly and you vote for a representative he might not vote for the person who would give free health care.
So in technicality no one has the right to vote for the president in first place. But now this is the excepted truth so to keep the idiots from winning we have go along with it.