WASHINGTON - Deputy Attorney General Eric Holder used to shoot hoops for Stuyvesant High in New York City, but these days, he tosses a blue "stress ball" at wood-paneled office walls. As Attorney General Janet Reno's top deputy in charge of the day-to-day operations of the Justice Department, Holder also is juggling political time bombs. He's at the helm of the campaign finance investigation and the potentially explosive review of the Rev. Martin Luther King Jr. assassination files. He's also quietly reviewing the independent counsel law.