Sen. Frank R. Lautenberg, New Jersey Democrat, returned to the Senate after an absence of two years. Now, former senator Bob Kerry of Nebraska, with whom Lautenberg served, is attempting a comeback. (Associated Press)

Sen. Frank R. Lautenberg, New Jersey Democrat, returned to the Senate after an absence of two years. Now, former senator Bob Kerry of Nebraska, with whom Lautenberg served, is attempting a comeback. (Associated Press)