Former Republican Sen. Rick Santorum criticized the letter's opening words, calling it "politically correct".  Really? 

This is the opening:
________________________________
Dear Mr. President -
Congratulations on a remarkable run. Millions have placed their hopes in you, and all of us, regardless of party, should hope for expanded prosperity and security during your tenure.
_____________________________

Conservatives are now just using "politically correct" when they can't think of anything pertinent to say.  Which is an awful lot of the time.

Nice letter from Obama, as one would expect.
Not really expected that someone would leak it to the press but apparently Trump loved showing it off.  Probably not reading it, but waving it about anyway.

http://www.cnn.com/2017/09/03/politics/obama-trump-letter-inauguration-day/index.html