Conor McGregor is doing a complete 180 on his feelings toward Donald Trump -- bashing the former president for calling Khabib Nurmagomedov his favorite UFC fighter and claiming the move is a serious deal breaker for him.
No. 45 sang the Dagestani fighter's praise during a live stream with Adin Ross on Monday ... and as soon as Notorious got wind of it, he ripped into Trump on X.
"Campaign ending decision," Conor said ... adding the right move would have been to deem an American fighter his favorite instead.