Kraft -- who supported Obama in 2012 -- issued a glowing statement about Trump to the Boston Globe ... saying he's been a "very close friend of mine for over two decades."
"While I am not comfortable discussing politics publicly, I am very comfortable talking about my friendships with people who happen to be in politics."
Kraft noted the two of them had "a lot of fun together socially, including a very memorable evening in 2005 when I had the privilege of being at his and Melania’s wedding."
But Kraft says the friendship is deeper than partying together ... saying Trump showed his true colors as a friend after Robert's wife Myra passed away in 2011.
"After my wife passed in 2011, he was one of the few people who went out of their way and went above and beyond to assist me through the most difficult time in my life."
"I will always be grateful to him for his thoughtfulness and his continued friendship."
Kraft is not the only Trump fan on the Patriots -- Tom Brady has said he really likes the guy ... but also wouldn't officially endorse him.