People do influence others with the intent of changing minds, but I think the usual way that this happens is when the agent of change actually believe that the story is true.
I see political parties as comprised of a large group of people, each of which has different goals. My guess is that most party leaders believe in one or more of the goals of the party, and don't really think of their marketing as lies or intentional deception.
We are sold the deception, but many of us want to buy into the deception. We need to take back our personal responsibility to understand ourselves and understand what's going on in reality.
We don't really know the intentions of a complex organization. I would agree with something like the above that happens without an intentional plan to deceive:
"We are deceived when we allow ourselves to be influenced by others without applying a process to filter out false statements. Many of us like something about the message and go along with bad arguments (this is belief bias). If we acquire the skills to understand which arguments can be reached by empirical evidence, we might be able to eliminate some of our false beliefs"
Yes, I'm sure most politicians believe the deceptions as truth or reality instead, and propagate it thus. Objectivity for sure helps in filtering out the non sense.