In mid-November, I went to hear Boris Nemtsov speak at Columbia University. A leading opposition figure, he began not by criticizing the Russian government but by stressing the importance of ratifying New START.

A few days later, at the NATO summit in Lisbon, defense ministers from former Soviet republics and Warsaw Pact countries — now NATO members and no friends of Russia — tried to impress upon U.S. journalists how vital it is to ratify this treaty, which will cut both sides’ strategic warheads by roughly 30 percent. But it seems that U.S. Republicans, who cut the Democratic majority in the Senate to a minimum after the November elections, will not allow a vote on its ratification to be held by the end of December, when the lame-duck session ends. When the new Senate convenes in January, Republicans will probably kill the treaty.

It is a remarkable show of U.S. weakness. As history demonstrates, a country’s strength is not measured by its number of fighter planes or aircraft carriers but by its ability to understand national interests, set national goals and act decisively to achieve them. The goal of the Republican Party is to make U.S. President Barack Obama a one-term president, and they are willing to sacrifice U.S. national interests to do it — and kill the economy and cohesion of society to boot.

Obama is also weak. In his place, President Franklin Roosevelt, for instance, would have torn his opponents to shreds had they handed him a powerful political weapon by revealing that they were willing to risk the long-term security of the nation for a blatantly partisan political purpose. Yet it seems that Obama and his Democrats have neither the guts nor the conviction to fight for U.S. national interests.

The United States faces major challenges in the world as well as in its domestic economy. What’s more, the country is entering a difficult period, one in which it is weaker than at any other time since perhaps the Civil War.

Meanwhile, a similar problem looms over Russia. Nemtsov’s Columbia speech was focused on Prime Minister Vladimir Putin and the corrupt political system he has created. But I couldn’t shake off the impression that, even though Putin’s system is still very much in place in Russia, his era is coming to an end. True, nothing has changed outwardly and no key political player has been removed. The state machinery is still firmly in place, and journalists and Putin critics are beaten up as before. But there are changes being made on the periphery, the language of the political debate is changing, and the shifting mood among most Russians suggests that the people are preparing themselves for a post-Putin world.

Few people would shed tears for Putin if he stepped down in 2012. The country will probably be better off without him. But the transfer of power in Russia has always been an extremely painful and uncertain process. Ever since the Bolshevik Revolution, it has involved turmoil and factional strife. Russia, too, is heading into a period of weakness.

Russia no longer plays a key role on the global arena. If it were Russia alone that was entering a period of instability, it would not have mattered quite as much.

But when both of the world’s military superpowers — the countries that control the lion’s share of the world’s nuclear arsenal — face an uncertain future, the world suddenly begins look like a very dangerous place.