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.