Representative Rashida Tlaib was supposed to headline an event called "Chomp the Oligarchy" for three candidates for Congress who face Jewish Democrats in Tuesday's primary.
Decades before his rise to the New York State appellate court, he was a probation officer who tried to help Mr. Oswald, then a teenager living in the Bronx.
Republican and Democratic challengers are both using the issue to attack members of Congress as unethical, seizing on a common practice that enrages voters.