While chastising us for supposedly meddling in his internal affairs, Mr. Putin expanded his campaign to weaken democracy abroad. Kremlin-aligned media like the TV station RT have championed his policies internationally, while challenging the legitimacy of democratic leaders, including our own president. Around the world, but especially in Europe, the Russian government supports — by both rhetorical and financial means — political parties and organizations with illiberal, nationalist agendas. Russia’s 2014 annexation of Crimea and its intervention in eastern Ukraine in support of separatists, as well as the invasion of Georgia in 2008, were violent efforts to destabilize new democracies.

Many are impressed and aim to copy the Putin playbook. Autocrats in Asia, the Middle East and Africa have emulated Mr. Putin’s draconian laws restricting civil society groups. The leader of France’s far-right National Front, Marine Le Pen, has praised Mr. Putin and his policies; her party has taken a $10 million loan from a Russian bank and seeks another $30 million for next year’s presidential election. Two champions of the Brexit campaign — Nigel Farage, the former leader of the anti-immigrant U.K. Independence Party, and Boris Johnson, a Conservative member of Parliament and now Britain’s foreign minister — have spoken fondly of Mr. Putin. So, too, does Hungary’s increasingly authoritarian prime minister, Viktor Orban. The Republican Party nominee for president, Donald J. Trump, has frequently praised Mr. Putin. “He’s a strong leader,” Mr. Trump said in December.

As well as overt means, Mr. Putin has deployed cyber methods of subversion. This week, WikiLeaks released emails stolen from the Democratic National Committee. This action by a foreign agent prompted the resignation of the Democratic National Committee chairwoman and raised new electoral challenges for the Democrats’ presidential nominee, Hillary Clinton. American intelligence agencies have “high confidence” that the Russian government stole the data — and likely also hacked into the Clinton campaign’s computer systems. While we can’t be certain yet whether its agents passed the data directly to WikiLeaks, the circumstantial evidence points overwhelmingly to Russia. Who else?

We also know that Russia’s use of signals intelligence to advance an antidemocratic agenda is not a new tactic. I have firsthand experience. During my stint as ambassador, Russian agents secretly recorded a conversation I had with American business executives at a Moscow hotel and published my remarks in a way to make it sound as if the United States was plotting against the Russian government. In 2014, an intercepted phone call between America’s ambassador in Ukraine and Assistant Secretary of State Victoria Nuland was leaked to suggest that Washington was choosing the new government in Kiev. Against Russian opposition leaders, the Kremlin deploys such tactics all the time.

Mr. Putin may be the boldest but he is not alone in this growing movement. China’s economic success challenges democracy’s appeal. Iranian theocrats hold on to power at home and defend autocrats like President Bashar al-Assad of Syria. Elsewhere in the Middle East, strongmen like President Abdel Fattah el-Sisi of Egypt are ascendant, forcing their citizens and foreign allies to accept their repressions as supposed protection from Islamist extremists. Saudi Arabia intervened in Bahrain to crush a democratic movement there in 2011, while private Arab foundations continue to promote illiberal ideas throughout the region and beyond.