They also plan to register voters and encourage early voting at Sunday's event.
King and Ronstadt, a Tucson native, will discuss why they support Kerry's positions on education, health care and the environment, Natalie Luna, spokeswoman for Rep. Raul Grijalva, D-Ariz, said this week.
Ronstadt praised documentary filmmaker Michael Moore at a concert in Las Vegas in July, causing some audience members to storm out. Moore's latest film, "Fahrenheit 9/11," is critical of the Bush administration.
King, known for songs including "It's too Late" and "You've Got a Friend," has campaigned for Kerry in 30 states since January.