Mueller’s testimony is vital — not just for 2016 but for the future, too

The raw partisan divide cleaving America and constantly worsened by President Trump is almost certain to be on full display Wednesday, when Robert S. Mueller III appears on Capitol Hill. The House Judiciary Committee, followed by the House Intelligence Committee, will hear Mueller’s testimony about the findings in his special counsel report on Russian interference in the 2016 presidential election.

Committee members on both sides of the aisle will have to contend with an inescapable conclusion from a fair reading of the report: The Russian attack would not have worked...