Sen. Jeff Flake, R-Ariz., tweeted a picture Tuesday of a $100 check intended for Democratic Alabama Senate candidate Doug Jones.
The note on the check, along with the text of Flake's tweet, contained the words "Country over Party."
Earlier in the day, White House press secretary Sarah Sanders defended President Trump's endorsement of Republican Senate candidate Roy Moore, saying it was up to the people of Alabama to decide.
In response, Moore asked for donations to his campaign, calling Flake "pro-amnesty" and "big gov't."
CALLING ALL PATRIOTS! Pro-amnesty, big gov't Republican Senator @JeffFlake just donated to my pro-abortion, open borders, anti-gun liberal opponent.
I'm asking for 100 grassroots conservatives to step up and reject the DC Establishment by donating HERE: https://t.co/ig9d3KOKn4 https://t.co/jFLUpwElqx— Judge Roy Moore (@MooreSenate) December 5, 2017
Jones thanked Flake in a tweet with "#RightSideOfHistory."
Moore faces numerous allegations of sexual misconduct with teenage girls while he was in his 30s. He denies those charges and has resisted pressure from within his own party to step aside.
Flake is a vocal critic of Trump's, a sentiment the president has repeatedly fired back in the senator's direction.