Lawyers have a cardinal rule: Don’t ask witnesses on the stand questions that you don’t know the answers to. The Dems might follow that advice regarding Bush’s National Guard service. Today’s story in The Post pretty much exonerates him, or at least reporter Josh White didn’t quote any credible skeptics. If the Dems keep suggesting Bush was AWOL and he comes up with irrefutable proof late in the campaign, their credibility is damaged. Quiet research is the better strategy.