CREDIT FOR the internecine furor that disrupted the Democratic Party on the eve of its convention should go to Vladimir Putin. As The Post has reported, cybersecurity experts say Russian intelligence operatives were likely responsible for the hacking of the Democratic National Committee’s computer network, as well as for leaking to the Moscow-friendly WikiLeaks website some 20,000 emails. The trove appeared online Friday, just in time to create discord between supporters of Hillary Clinton and Bernie Sanders as they headed to Philadelphia. To no one’s surprise, the emails showed that DNC staffers opposed the attempt of the socialist Mr. Sanders to take over the party. Chair Debbie Wasserman Schultz was forced to announce her resignation, and — as Russia likely intended — Ms. Clinton’s campaign took a hit.

Mr. Putin’s regime has tried to intervene in the internal politics of numerous European countries, from Ukraine and Moldova to Italy and France. But the evident attempt to meddle in a U.S. presidential election is a first. That may reflect the reckless aggressiveness Mr. Putin has embraced in foreign affairs since returning to the presidency in 2012. It likely also reveals Moscow’s judgment that it stands to reap a geopolitical windfall if Donald Trump is elected president.

The potential benefits Mr. Trump offers to Mr. Putin have been clearly and repeatedly spelled out by the candidate himself. Russia’s most cherished goal is to weaken or destroy NATO; Mr. Trump has called the alliance obsolete. Mr. Putin dreams of reestablishing dominion over the pieces of the Soviet Union; Mr. Trump has said that he might not defend former Soviet republics Latvia, Estonia and Lithuania if Russia invaded, despite their NATO membership. Mr. Putin wants the United States to treat Russia as an equal superpower with its own acknowledged sphere of influence; Mr. Trump has repeatedly praised Mr. Putin and promised to work with him.

This pro-Kremlin tilt is unprecedented in the Republican Party and would represent a radical and dangerous shift in U.S. policy. Whether there are non-political reasons for it is a fair question. Mr. Trump is known to have sought business repeatedly in Russia, and his son Donald Jr. has said that “Russians make up a pretty disproportionate cross-section of a lot of our assets.” Because Mr. Trump will not release his tax returns or business records, the full extent of his financial interests in Russia remains unclear. But at least three of Mr. Trump’s top advisers have profited from business and political connections in Russia, including campaign manager Paul Manafort, who worked for the former pro-Putin president of Ukraine as well as several Russian oligarchs.

One of the few changes in the GOP platform pushed by the Trump campaign was the weakening of language calling for support for Ukraine’s current democratic government, which replaced the man Mr. Manafort represented — and which Mr. Putin is attempting to destroy. The DNC emails appeared on WikiLeaks the next week.

Some political analysts doubt that KGB-style tricks will ultimately sway votes in a wide-open U.S. election — especially as Moscow has barely bothered to disguise its authorship. Yet the fact that Mr. Putin is trying is remarkable and disturbing — as is the motivation Mr. Trump has given him to meddle.