"Chief Justice John Roberts presided over President Trump's first impeachment trial, but now that Trump is a former president, Roberts is not constitutionally obligated to preside. "
no Constitutional basis whatsoever. bordering on insurrection, certainly a violation of the Oath of Office.
https://www.npr.org/2021/01/25/960389715/sen-patrick-leahy-to-preside-over-trumps-senate-impeachment-trial