evidence: ProPublica did find that challenges sometimes identified errors in the voter rolls, which are dauntingly complex databases that are forever evolving as people register, move, die or otherwise change their statuses. Many of these corrections would have happened anyway in the routine maintenance process, officials said and records showed, though sometimes at a pace slower than if activists submitted challenges. "If all these challengers are finding is inconsequential errors that do not affect election results on the whole, but they’re placing real and harmful burdens on voters, then you have to wonder why they’re really doing this," said Derek Clinger, a senior staff attorney with the State Democracy Research Initiative at the University of Wisconsin Law School. "It’s doing more harm than good." [...] Despite requests from some counties for clearer direction, state officials have issued limited guidance for how counties should handle challenges, mostly advising them to rely on their attorneys.