Movie stars, recording artists, and others from the performing arts are constantly in the news with their efforts to influence Congress, voters, or charitable contributors. Recently it was the turn of some fairly second-tier actors like Alec Baldwin and Melina Kanakaredes (both of the wooden stump school of acting) to appear before Congress to argue for more funding for the National Endowment for the Arts and the National Endowment for the Humanities.
I wonder if anyone has ever analyzed the effectiveness of these intercessions. My guess is that when Congress is the audience, such gigs have almost zero effect on members' votes, but they do help put boring old Congress in the limelight for a half-day or so. The verdict is a little less certain when it's a matter of a star performing for the benefit of an individual politician - at a fundraiser, for example. There too, I suspect negligible practical effect, though I am sure there must be some voters whose minds can be swayed by the inference that favorite singer Sirenia Squawker likes John Whitebread for Congress. After all, why shouldn't a performer be just as influential in these matters as equally irrelevant pastors or tribal leaders?
No doubt performers' best chance at having impact is to connect his/her name, reputation, and bank account with a charitable or humanitarian cause. Not that they influence political action as such (though they do try) but they can attract attention and contributions to a cause that hasn't had much publicity. Most of our media quickly get bored with starving refugees, but a star's trip to visit those same refugees can refocus the spotlight for a day or two.
In all cases, it helps to keep in mind that the primary beneficiary of a performer's appearance for a "cause" is probably ... that performer.