MOSCOW — The diatribe against the Obama administration on prime-time television by a Russian Foreign Ministry official was hardly unusual in the long history of rocky relations between the United States and Russia.

The administration “demonstrated the belief that the strongest has the right to create evil,” Maria Zakharova, the Foreign Ministry spokeswoman, said on the Christmas Day broadcast.

From Washington’s perspective, it is the Kremlin that generally personifies evil, a point President Obama made on Thursday in punishing Russia for cyberattacks by directing new sanctions against Moscow and expelling 35 Russian diplomats. “The United States and friends and allies around the world must work together to oppose Russia’s efforts to undermine established international norms of behavior,” Mr. Obama said in a statement.

The two statements appeared to be business as usual — each side representing enemy No. 1 for the other. By Friday that mood had been abruptly cast aside, however. President Vladimir V. Putin announced that Russia would do nothing in response to the new American measures, awaiting the next administration, prompting President-elect Donald J. Trump to call him “very smart” in a Twitter post.

With the sitting president calling Russia a national security threat and the incoming one praising Mr. Putin, many American voters, long accustomed to being suspicious about Russia, are understandably confused and uneasy. Russia was an enemy on Friday morning, and a friend by the afternoon.

“We are in a whiplash moment right now, and I think it is unprecedented in several respects,” said Cliff Kupchan, the chairman of the Eurasia Group, a political risk assessment firm in Washington, and a former State Department official from the Clinton administration. “The most important one is that the baton is about to be passed from an administration with a very hard line on Russia to one that is very much more sympathetic.”

No clear agreements or even offers are on the table yet, however, bringing uncertainty. “Russia’s relations with the U.S. are currently up in the air — both sides have no clear strategy about how to move them forward,” said Aleksandr Morozov, an independent Russian political analyst.

Until the Soviet Union collapsed in 1991, and even for years afterward, matters were more black and white. A young American diplomat stationed in Moscow named George F. Kennan established the parameters of the relationship for decades with a famous 1947 policy paper. The Soviet Union was bent on expansion, he wrote, so the main element of any United States policy had to be containment.

Thus began a long roller coaster ride for the two countries, full of periodic upswings as friends when détente was in vogue, inevitably followed by precipitous plummets as foes that left the world shuddering about the prospects of a nuclear Armageddon.

Tensions eased periodically, but it never seemed to last.

President Ronald Reagan, an implacable anti-Communist, surprised the world by reaching out to the man who turned out to be the last leader of the Soviet Union, Mikhail Gorbachev, to begin negotiations for far-reaching arms control agreements between the two sides.

After the Soviet Union collapsed in 1991, the Russian Federation that emerged entered into an extended period of decline and, inevitably, friendship with the United States as a kind of junior partner.

That “junior” aspect rankled, however, particular after Mr. Obama went from seeking to reset relations to dismissing Russia as a “regional power.”

The latest crisis began in 2014, with a revolution in Ukraine that Mr. Putin labeled an American plot — he, as many Soviet leaders have, sees the hidden hand of Washington everywhere. Mr. Putin annexed Crimea and armed rebels in eastern Ukraine, prompting Western economic sanctions, which Mr. Trump has disparaged.

The last confrontation…