For his part, Mr. Trump has already warned North Korea against “interference,” though he appeared to be referring to missile launches meant to embarrass him.
The president has shown far less concern about Russian interference. He has repeatedly questioned the idea that Moscow meddled in the 2016 election, viewing such talk as a challenge to his legitimacy. In his zeal to find another culprit, Mr. Trump eagerly embraced a Russian-backed conspiracy theory that shifted the blame to Ukraine, and set in motion the events that led to his impeachment.
American officials, however, are nearly unanimous in the conclusion that Russia interfered in 2016, and that it remains the greatest threat in 2020. Unlike other countries, which are seen as eager to influence American policy, Russia appears, above all, to be interested in undermining confidence in America’s democratic institutions, starting with the voting process.
Then and now, officials and experts said, the Russians and others could bank on one constant: America’s partisan divide, which engenders deep cynicism among Democrats and Republicans alike.
“Our adversaries, including Russia, China, Iran and others, are persistent: They focus on our politics and try to take advantage of existing fissures and American sentiment, particularly if it may weaken us,” said Shelby Pierson, who monitors election threats at the Office of the Director of National Intelligence.
“They’ll try many tactics and can adapt,” she added. “If it doesn’t work out, they try something else.”
In the public imagination, the defining elements of Moscow’s interference in the 2016 election were disinformation and the hacking of Democratic Party emails. But as they look to 2020, many election security officials and experts say the most worrying piece of the Russian meddling was the hacking of state election systems.