How we change what others think, feel, believe and do
If your words might lack credibility in some way, borrow the credibility of others by getting the testimony of trusted others.
Use celebrities and public personalities who have well established and trusted public brands. Use experts, clerics, police, scientists and others whose title is respected, even if the people themselves are unknown. Use people who are like the people whose support you need.
Get them to stand up and support your case with vigor. Get them on stage with you. Get them on TV shows and into political debates. Help with with words, if you can (but do not alienate them by being too pushy).
In my last movie, I saved my family from terrorists and I'm supporting this party because they will save you from terrorists!
I am a doctor and I say this man would have died had he not got the right medicine in time. And I ask you, where did that medicine come from?
Political parties know that a celebrity testimonial is worth many votes. They also make great use of testimonials from ordinary people to show that people like your and me. Advertisers, too, make great use of celebrities and credibly ordinary folks.
With 'experts', listeners often do not know of their real credentials, yet still accept the expert's authority. They will seldom question this matter, particularly when the content distracts them from this questioning. Claims of expertise are thus often used to boost credibility of statements.
Actors, perhaps unsurprisingly, often do testimonials particularly well. It is hence common to see actors supporting political parties and others who are using this method.
Testimonials need not be true or honest. You can pay people to say pretty much anything, and some will be happy to say whatever you like for a suitable sum. Be careful about paying, even for genuine support, as if it is found out then it will devalue the testimonial and possibly be seen in a very negative way.
Clyde Miller, Propaganda Analysis, NY: Institute for Propaganda Analysis, 1937