They used it in the time frame because he was not President at the time.
These impeachment threats are created out of whole cloth, sort of like rock soup.
Good PR opportunity as lead up to his senate run.
https://www.npr.org/sections/publiceditor/2011/10/12/141293477/why-do-you-call-him-mr-obama
Read away.........
The rule is they refer to ant President Trump by his formal title and after that they refer to him as Mr.
Does the NY Times, realized Mr. Trump is known as
PRESIDENT TRUMP ???
THAT SO CALLED NEWS PRINT IS TOTALLY WORTHLESS...
It has always been the policy of the New York Times to refer to the President as Mr., in every administration. I have noted it all my life, and thought it was stupid and disrespectful, as well as incorrect, all my life.
I remember NPR in 1991 calling Bush Senior “Mr. Bush” over and over, then switching to a deferential “the president” two years later when Clinton got elected.