The Constitution gives the House the sole power of impeachment, but it doesn’t outline specifically how to get there. Congress has engaged in impeachment proceedings against a president three previous times.

All have included a House-wide vote to open an inquiry, but so far, the Democratic-led House has resisted that approach. Earlier this month, the House Judiciary Committee established procedures to allow it to determine by the end of the year whether to recommend articles of impeachment against President Trump. With House...