But what it also means is that, you may not be allowed to display your beliefs. A shirt, or a hat may get you into a fight, a yard sign may get your house vandalized, a bumper sticker may get your car keyed, or working as a canvasser may get you attacked.
You essentially have to choose between openly showing your support for someone, and risk retaliation, or keeping it hidden, and not being able to spread the word and try to help your party win.
As we can see, being forced to be silent about politics can affect reach, and thus can affect votes. If you are afraid to be able to wear campaign garb, or display a yard sign, you are forced to stop helping your candidate effectively advertise, or, get their name out there. When people see a downturn in things like that, it gets translated into polls, and news stories report it as low support for something. That can actually influence minds...and votes....
Voting, and support for a political party is one of our most fundamental things in this country. Why should someone be forced to be silent about their political leanings?
What stifles engagement is being afraid of showing your support for someone for fear of some kind of harassment or being attacked.