In a reversal, President Trump appears to have backed off joining a European push for new sanctions on Russia, seemingly eager to move on to doing business deals with it. For months, President Trump has been threatening to simply walk away from the frustrating negotiations for a cease-fire between Russia and Ukraine. After a phone call on Monday between Mr. Trump and President Vladimir V. Putin of Russia, that appears to be exactly what the American president is doing. The deeper question now is whether he is also abandoning America’s three-year-long project to support Ukraine, a nascent democracy that he...