ROBERT C. O’BRIEN, the White House national security adviser, asserted recently that “no administration has been tougher on the Russians.” Secretary of State Mike Pompeo told the Senate Foreign Relations Committee on July 30 that “we’re the toughest administration ever on Russia.” They have one colleague, however, who has displayed no toughness toward Russian leader Vladimir Putin: President Trump. Now would be a good time for him firmly to discourage any Kremlin military intervention in Belarus.

Belarusan President Alexander Lukashenko’s theft of the Aug. 9 election, and his violent crackdown thereafter, has ignited a popular revolt, including strikes at the huge state enterprises. Even news broadcasters are on strike, demanding the right to tell the truth and calling for new elections. On Monday, the longtime autocrat suffered the indignity of being jeered off the stage by factory workers. In desperation, Mr. Lukashenko twice telephoned Mr. Putin over the weekend and claimed to receive statements of Kremlin support.

Mr. Trump, whose obsequiousness toward Mr. Putin remains a riddle, should make clear to him that this is not a moment to repeat Russia’s disastrous military intervention in Ukraine. Mr. Putin may not need much convincing. Surely, he would like Belarus to remain under Russia’s wing, and he has a strong allergy to any display of popular will. But Mr. Putin’s own political standing inside Russia is weak — witness the mass protests in recent weeks in Khabarovsk — and he hardly needs more discontent at home. Any military intervention would require a large commitment of forces and face popular resistance. Mr. Putin seems to have little personal affinity for Mr. Lukashenko, who has always tried to play Russia against the West. Still, the situation in Belarus has no easy answers for Mr. Putin: He does not want to embrace a flailing and failing dictator, but nor can he welcome an example of democratic success on Russia’s border.

Meanwhile, U.S. leaders are responding to the upheaval in Belarus with excessive timidity. Perhaps Mr. Pompeo remains nostalgic for his Feb. 1 trip to Minsk, where he sought to coax Mr. Lukashenko into leaning a bit toward the West. Whatever the merits of the strategy then, it has now been vaporized. In Poland on Saturday at a news conference with Foreign Minister Jacek Czaputowicz, Mr. Pompeo said “we urge the leadership of Belarus to broaden the circle” and “to engage with civil society in a way that reflects the central understandings that the Belarusan people are demanding.” But Mr. Lukashenko’s moment for “broadening the circle” has passed. The popular revolt in Belarus should result in the peaceful transfer of power to those who won the election, led by opposition candidate Svetlana Tikhanovskaya, followed by releasing political prisoners, lifting all restraints on free expression and holding truly free and fair elections.

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