Alexei Navalny’s Illness Latest Blow to Russia’s Struggling Opposition

MOSCOW—The sudden and mysterious ailment that remaining Kremlin critic Alexei Navalny in a coma has sent a blow to Russia’s political opposition, throwing into dilemma its foreseeable future at a time when the Kremlin has stepped up its efforts to stamp out dissent.

Mr. Navalny fell sick on a flight from Siberia to Moscow final week right after drinking a cup of tea that his supporters say was laced with poison. He was evacuated to a Berlin healthcare facility on Saturday. Medical practitioners there haven’t disclosed any details of his situation or what they believe…