To the surprise of nobody, Trump’s attorneys are arguing that his statements at the rally preceding the riot do not meet the “incitement” exception in First Amendment jurisprudence, and so he cannot be convicted on the impeachment article. Let’s leave the premise aside, for now; is the conclusion correct? Is the legal standard for impeachment identical to the one which prohibits criminal prosecution for words short of “incitement,” as that term has been defined in case law?
It’s not a ridiculous argument, but I don’t think so. The balance of private rights and public harms in impeachment is different than in a criminal prosecution. The liberty interest deprivation (loss of office versus the loss of physical freedom) is less compelling, and the public interest in the protection of the constitutional order is greater when a rogue president is involved, rather than an average citizen. Congress is consequently free to adopt a lower standard for impeachment proceedings if it chooses to do so.
I would imagine Trump would contend that leaving the usual First Amendment standard creates a slippery slope that will ultimately lead to instability and disaster. The truth is, however, that the combination of partisan politics and the two-thirds conviction requirement provides more than enough protection for future presidents from frivolous impeachment proceedings. Impeachment has already been shown to be a weak reed; the impending Trump acquittal will only make that more clear.