Eleanor Clymer is one veteran juvenile author who's managed to keep abreast and to keep smiling. ""Last year,"" 14-year-old narrator Kathleen Rowan confides, ""I opened my mouth and changed our lives."" Kathleen's homemaker-mother was a doer--""always involved in something."" She'd majored in biology, took an interest in conservation, had answers to the kids' questions about how politics worked. Best-friend Debbie is impressed. Then, after a Village Board meeting, at which Mom puts the Mayor on the spot, and a class session, at which the Mayor fumbles the kids' questions: ""I bet your mother could answer those questions. She's smarter than Mayor Hennessy."" So, at dinner, Kathleen comes out with it: ""You ought to run for mayor."" What ensues is a perky course in practical small-town politics, with some natural domestic complications--and a crucial role for Kathleen. Mom, in jeans and ponytail, ""doesn't look like a mayor,"" she hears from the other kids. (""Suddenly I knew something. How you look is what people think you are."") She proposes new duds--a suit, shoes with heels--and a new hairdo. ""We stood looking each other in the eye for about a minute . . . as if [I] were not just her child but an equal."" Finally: ""All right. We'll give it a try."" Later, somewhat more prosaically, Kathleen publicly defuses the charge that ""mothers should stay home and take care of their children."" And, with all that she's learned, ""Maybe I'll be in politics myself when I grow up."" Spirited and instructive it is--and jauntily illustrated too.