Hillary Clinton adopts Southern Accent

Everyone does that to some extent. You speak to your teachers differently than you speak to your friends, for example.

As everyone knows, Marlon Brando was widely considered to be one of, if not THE, great actors of his generation. I read one of his rare magazine interviews in which he downgraded his own talent, and the acting profession as a whole, contending that acting is merely "behavior," and that practically EVERYONE "behaves" differently at different times depending upon whom they're with.

Everyone "acts" a certain way around their boss, but differently around their children, and yet another way with their own parents.

Certainly this is true of politicians. It could be reasonably argued that all successful politicians are good actors to some extent, because they need to engage thier "audience," be they national television viewers, a large crowd of constituents, an influencial business person, or a foreign head of state.

Woody Allen took this phenomenon to its humorous, touching, and satirical extreme in "Zelig." This is perhaps my favorite among his efforts.