Hours before Donald Trump appeared Tuesday at a Miami courthouse and pleaded not guilty to charges related to the handling of sensitive government documents, the chairman of Nevada’s Republican Party walked into the federal trial court in Washington. Michael McDonald’s presence there alongside Jim DeGraffenreid, the state GOP vice chairman, underscored advances in special counsel Jack Smith’s other federal inquiry: the one into efforts by Trump and his allies to overturn the 2020 election. McDonald and DeGraffenreid were among the latest in a string of witnesses summoned to testify before a grand jury in that investigation, people familiar with the...