Graham appeared on Fox News Thursday and called for someone in Russia to "step up to the plate" ... "The only way this ends is for somebody in Russia to take this guy out. You would be doing your country and the world a great service."

Graham was direct, asking, "Is there a Brutus in Russia? Is there a more successful Colonel Stauffenberg in the Russian military?"

Graham then doubled down in a tweet ... “Unless you want to live in darkness for the rest of your life, be isolated from the rest of the world in abject poverty, and live in darkness you need to step up to the plate."

Putin has become a despised war criminal who is randomly killing innocent civilians, flirting with nuclear reactor disaster and destroying a country. He's also become extremely unstable and paranoid.

The problem -- several problems -- what Russia and the world could end up with could be even worse. Maybe more to the point ... it's dangerous for American leaders to call for the assassination of a head of state. It's hard to maintain moral high ground when we call for the violent overthrow of another government. We should've learned that from the Bay of Pigs.

Graham's remarks drew fire from both parties. Rep Ilhan Omar tweeted, "I really wish our members of Congress would cool it and regulate their remarks as the administration works to avoid WWlll."