Eric Schmidt, billionaire chair of Alphabet, Inc. the parent company of Google, led a massive fundraising drive in December for leftist analytics firm Civis Analytics, represented by a law firm that partnered with Justice Department special prosecutor Robert Mueller—raising questions about Mueller’s impartiality in his so-called “Russia probe” into President Donald J. Trump’s campaign. In March 2014, WilmerHale announced Mueller would join its firm as a partner. Mueller left his position in May after the DOJ appointed him as a special prosecutor to look into alleged “ties” between President Trump’s campaign and Russia. WilmerHale represented Civis Analytics during a $22...