In one of the nation's hottest congressional races, Howard Berman and Brad Sherman are stepping up their attacks on each other. Because of California's new election laws, the two Democrats are running for re-election in November's election for the same Congressional district in the San Fernando Valley. As the race has gone on, it's become nastier and nastier. Last week, at their first debate since Sherman came in 10 points ahead of Berman in the June primary, an audience of about 400 people cheered and booed both candidates. One person told the Daily News he'd come to learn their differences not to see a "boxing match." Jonah Lowenfeld is covering the race for the Jewish Journal.