By Guy Faulconbridge
LONDON (Reuters) - President Vladimir Putin has been weakened by his decision to invade Ukraine, but a change in power at the top in Russia is unlikely any time soon due to the autocratic nature of its political system, a Western official said on Wednesday.
Putin, the longest-serving paramount Kremlin leader since Josef Stalin, has dominated Russia for nearly 23 years since Boris Yeltsin gave him the nuclear briefcase on the last day of 1999.
After changes to the constitution in 2020, some Russia-watchers expected Putin to rule until 2036. But the Feb. 24 invasion of Ukraine has changed perceptions.
"He has been weakened by this really catastrophic error," said the Western official, who spoke on condition of anonymity in order to speak freely. "We are seeing the Russian military humbled on the battlefield by Ukraine."
The official said the war had strengthened Ukrainian statehood and prompted the further enlargement of the NATO military alliance thus weakening Putin, who turned 70 on Oct. 7.
"People can see that he has made a big error," said the same official. "They (the Russians) didn't have a Plan B - they thought that this was going to be really easy."
"That has to mean that people are talking more about succession, they are talking more about what comes next, they are imagining a life beyond. But what I am not doing is suggesting that that's any time soon."
Though there was unlikely to be a change of Kremlin leader soon, the official said that the middle of the 2020s was starting to look "more interesting".
Russia's next scheduled presidential election is in 2024. Putin has not yet said whether he will run again or not.
The Kremlin, which declined immediate comment on the Western official's comments, says Putin is by far the most popular politician in Russia and has won four presidential elections.
Putin has said he has no regrets on launching what he calls Russia's "special operation" against Ukraine and casts the war as a watershed moment when Russia finally stood up to an arrogant Western hegemony after decades of humiliation in the years since the 1991 fall of the Soviet Union.
After the West imposed the most severe sanctions in modern history on Moscow due to the war, Putin says Russia is turning towards Asia, and in particular China, after centuries of looking to the West as the crucible of economic growth and technology.
The war in Ukraine has killed tens of thousands and triggered the biggest confrontation with the West since the 1962 Cuban Missile Crisis, when the Cold War superpowers came closest to nuclear war.
Both Ukrainian and Russian forces are digging in for winter as temperatures start to fall, and the war is likely to continue to be "a long, difficult and bloody conflict", the official said.
After Putin's Sept. 21 partial mobilisation order, at least 400,000 Russians have left the country in addition to the outflow of Russians who left shortly after the invasion was ordered, the official said.
Russia's economy, they said, would contract by at least 4.5% in 2022 and would also contract next year, the official said.
"The [GDP] figures mask a really significant distortion in the economy because of the switch towards war production," they said.
The official added that there was no sign, for now, that Russia was ready to seriously negotiate over Ukraine.
"This is going to continue to be a long, difficult, bloody conflict."
(Editing by Andrew Osborn)