President Bush found time to campaign for Arlen Specter in a GOP primary last month. So why hasn’t he gone to South Dakota to help Larry Diedrich, the Republican candidate in tomorrow’s special election for the state’s single seat in the House of Representatives? Democrat Stephanie Herseth is said to be leading in the polls, but South Dakota is Bush country–the president might rally the base and push Diedrich to victory. (The special election is to replace Bill Janklow, the Republican who just went to prison for vehicular manslaughter.) If Herseth prevails, it would mark the second time in a row Democrats have triumphed in one of these House special elections–something that Republicans had been very good at doing in the 1990s. That’s a disturbing trend. A Herseth win also would bode poorly for John Thune’s challenge to Tom Daschle–polls show a close race, with Daschle consistently under 50-percent and Thune just a couple of points behind. Most important, however, is the fact that South Dakota’s House seat is an incubator for greater things because it’s bascially a statewide election. Successful candidates are well positioned to run for the Senate or governor later on. So if someday we’re scratching our heads and wondering why South Dakota keeps sending Sen. Herseth back to Washington, at least we should know how it got started.