Donald J. Trump made history on Wednesday as the first president to be impeached twice. After four years — and several decades – of saying whatever he wants, it will be a matter of speech that lands the final blow. He is charged with incitement of insurrection for spurring on the mob that stormed the Capitol on Jan. 6, 2021. The charge of “incitement” has been deployed many times in the past, often directed at agendas far different from Trump’s. On Sept. 12, 1918, Eugene V. Debs, the socialist presidential candidate, was convicted of attempting to incite subordination to the American armed forces and “uttering language to incite, provoke and encourage resistance to the U.S.” for an antiwar speech he delivered in a city park in Canton, Ohio.