There isn’t any unless it is accidental. There is a reason why it works out this way. The objective is to get elected. Politics is also the most ruthless activity on the face of the earth. The truth has no variance so a truth teller can use no variation in trying to get a point across. If candidate A tells the truth and gets a decent response. (In actual practice the truth will get a candidate booed off the stage.) To sound a little better, Candidate B, will change the truth just a little so the voters will like his version a little better. At that point it it is no longer the truth. It is a type of arbitrage.
Why do people believe politicians? In the mind of a listener, what constitutes the truth? Tell the listener what he wants to hear, and to the listener that will be the truth. It will be a counterfeit truth so no brownie points are made with God. It won’t be the truth but the listener will accept it as the truth.
Every successful politician knows how to create a mood where people will believe what they are told. An old staple in lye telling technique is to convince your victim that you like him and hold him in high regard. People are many times more likely to believe what they are told if it is told by someone who they believe likes them. Notice that every political speech starts with the politician telling the audience what wonderful people they are.
Telling the truth contributes nothing towards a positive outcome to a campaign so politicians stay away from it.
In politics, all words have the same value. All sentences have the same value. The politician uses the combination that best accomplishes his goal.