Hillary Clinton put on a terrible fake Arkansas accent for the beginning of her political career, talked about baking pies, and quoted country-western songs in interviews. The reason she uses her natural accent in her later career is because she has positioned herself as a "wonk," and often against Republicans who were doing folksy.

i.e. she's looking for a different set of Americans to "fall for it." Trying to appeal to an audience who thinks that everybody else is a sucker and they're the shrewd one.

When she goes to black churches, she puts it on again. Instantly starts dropping her g's and praising the lord like she would never do in a white church.