In recent decades, you could make a good living betting on American military intervention in any foreign crisis covered by CNN. President Obama has resisted demands to escalate our response to Russia’s aggression against Ukraine, but his resistance may soon collapse.

It has been under great pressure for months, with Republicans accusing him of being “weak and indecisive.” This week, a report from three establishment-oriented think tanks — the Atlantic Council, the Brookings Institution and the Chicago Council on Global Affairs — said the United States should provide “lethal defensive arms” and other supplies to the Kiev government. Ashton Carter, nominated to be secretary of defense, said in his confirmation hearing Wednesday, “I’m very much inclined in that direction.”