With early voting — finally — starting in Chicago’s elections, the race for 13th Ward alderman ended up in federal court Monday, with challenger David Krupa alleging that Ald. Marty Quinn and House Speaker Michael Madigan broke the law in working to keep him off the ballot. In the mayoral race, rivals Toni Preckwinkle and Susana Mendoza traded barbs over ethics. Meanwhile, Gery Chico made a play for the votes of snow-weary Chicagoans.