Sen. Jeff Flake shared a photo of a mug he said was left on his door on Christmas Eve, printed with the words "Decency wins."

"This mug was left at my door today. Thank you. What a thoughtful Christmas gift," the Arizona Republican tweeted.

They're the same words Flake tweeted after Alabama Republican Senate candidate Roy Moore was defeated by Democrat Doug Jones, for whom Flake publicly wrote a check.

Flake announced in October that he will not seek another term, blaming the "degradation of our politics."

"Reckless, outrageous, and undignified behavior has become excused and countenanced as 'telling it like it is,' when it is actually just reckless, outrageous, and undignified," Flake said on the Senate floor. "And when such behavior emanates from the top of our government, it is something else: It is dangerous to a democracy. Such behavior does not project strength, because our strength comes from our values. It instead projects a corruption of the spirit, and weakness."

Flake said Sunday that he isn't ruling out challenging President Trump in 2020, saying it's "not in my plans" but "I don't rule anything out."