Well, you are right. But that isn’t how it works. Remember, those constituents may have wanted whatever their President wanted too, but in order to get it, the Bill has to make through Congress.
That is where the wheeling and dealing go on. There are very few that haven’t participated in the sausage making at one time or another, which is why I mentioned that is it difficult when a Congressman or Senator runs for President. Of course the same doesn’t hold if you are a Democrat.
If the Pres and his constituents both want it, no problems then, but too many politicians sell out their constituents for the good of the party. This can be seen every day, just look at the government debt.