Sen. Jeff Flake of Arizona on Sunday warned fellow Republicans not to “succumb” to “political tribalism” by supporting Roy Moore, the party’s nominee for Alabama’s Senate seat who is accused of sexual assaulting and dating teenagers.

“After what we know, for Republicans to support Roy Moore over Doug Jones is political tribalism at its worst. We shouldn’t succumb to it,” Flake said in a tweet.

Flake's tweet came hours after President Trump wrote a tweet in which he ripped Democratic candidate Doug Jones as a potential "disaster" for Alabama’s Senate seat. Flake is a frequent critic of the president and is not running for re-election in 2018.

Trump has split from Republican lawmakers by refusing to criticize Moore, who is under siege after multiple women alleged Moore either sexually assaulted them or attempted to date them when they were teenagers and Moore was in his 30s.

Moore has denied all the allegations.

Republican lawmakers have mostly called on Moore to drop out of the race if the allegations are true.

Some Republican senators have said the upper chamber should expel Moore if he is elected.

Trump, meanwhile, has come close to endorsing Moore and repeatedly said Moore denies the charges.