Second, other pro-Putin, anti-E.U. politicians and movements throughout Europe just became a little stronger. Marine Le Pen, whose National Front party is partially financed by a Kremlin-friendly Russian bank, celebrated the U.K. referendum result. Other nationalist, xenophobic, isolationist leaders and parties on the continent who share her views already have begun to call for E.U. exit referendums in their countries. Even the process of debating these initiatives will weaken European unity. And here in the United States, it is no coincidence that presumptive Republican presidential nominee and Kremlin favorite Donald Trump has lined up with Le Pen and her ideological allies in praising the U.K. referendum result.

Third, new doubts about the utility of E.U. membership also weaken Putin’s opponents in Ukraine. Those who amassed on the Maidan in fall 2013 were demanding the very thing that British voters rejected — closer ties to the European Union. The ideas of these pro-European voices inside Ukraine now will face increasing scrutiny from E.U. skeptics, who will ask why Ukraine should seek to join a club that others are leaving. This same debate will play out in other countries contemplating E.U. membership.

Fourth, America’s closest ally when voting in multilateral forums, pressing diplomatically on global security issues and championing democratic values just became a little weaker. That’s a win for Putin. And who knows when the damage will end.