MOSCOW — President Vladimir V. Putin announced on Wednesday that he would seek a fourth term as president of Russia in a March election that he is expected to win handily.
A full, six-year term until 2024 would make his 24-year tenure — including his years as prime minister — the longest by a Russian leader since Joseph Stalin sat in the Kremlin for 29 years. It is widely believed that Mr. Putin wants to use what should be his last term, barring further constitutional changes, to cement his place as one of the more important historical figures ever to rule Russia.
It has been a somewhat improbable run for Mr. Putin, 65, who spent the bulk of his early career as a middle-level K.G.B. agent in East Germany.
Calling the collapse of the Soviet Union one of the greatest catastrophes of the 20th century, he has built his formidable popularity on the idea that Russia should restore its natural destiny as a superpower, an equal to the United States in military might and global influence.
His crowning achievement in pursuit of this goal was the 2014 annexation of Crimea, which has kept his popularity ratings around 85 percent ever since. Election day was moved to March 18, the fourth anniversary of that annexation, as a pointed reminder to voters.
Mr. Putin made the long-anticipated announcement on the floor of a vehicle factory in the northern industrial city of Nizhny Novgorod. He delivered a brief statement in the seemingly spontaneous yet carefully choreographed manner he favors for major appearances broadcast live on state television.
It began with a worker climbing onto the stage set up for the occasion at the Gorky Automobile Factory — known by its Russian acronym as GAZ — to ask Mr. Putin if he would run, saying: “Today in this hall everybody, without exception, supports you. Give us a gift, announce your decision!”
Asked the same question on live television at national forum for volunteer youths just hours earlier, Mr. Putin had said he was still thinking about it.
This time, with the hall erupting in cheers of “GAZ supports you!,” Mr. Putin said he was running. “There is no better space and no better occasion to announce this,” he said. “I will run for the presidency of the Russian Federation.”
The choice of venue and the occasion highlighted Mr. Putin’s support base — workers of Russia’s big industrial enterprises. During the street protests in Moscow in 2011-12, workers at a similar plant in central Russia offered Mr. Putin their help in dispersing anti-Kremlin protesters.
Mr. Putin is expected to cruise to re-election, not least because of his popularity and the lack of serious challengers. In fact, the main concern in the Kremlin now, according to political analysts of all stripes, is that the lackluster slate of candidates could drive turnout to historic lows and deprive Mr. Putin of a resounding mandate.
But there is no denying Mr. Putin’s popularity. The 2014 Winter Olympics in Sochi, Russia, dominated by Russia with 33 medals, also fueled his ratings. The scandal over state-backed doping, which saw Russia barred from the 2018 Winter Games, only seems to have bolstered his standing, as it fits into his narrative of Russia as a besieged fortress surrounded by enemies on all fronts.
Domestically, Russians experienced instability and poverty after the 1991 collapse of the Soviet Union. After assuming the presidency in 2000, Mr. Putin brought stability and an extended period of prosperity, with Russians gaining more household income in the first eight years of his term — mostly because of rising prices for energy, the country’s main commodity — than during any other period in their recent history.
That has gone into reverse in recent years, since the 2014 collapse in the price of oil and the ruble. But Russians have yet to blame Mr. Putin personally.
If anything, his popularity has been inching upward since the summer. A poll by the Levada Center in September showed 52 percent of voters supported him overall and 64 percent among those who said they would vote. The poll was based on 1,600 people questioned on Sept. 15 to 19, the center said.
His strongest rival, Aleksei Navalny, an anticorruption crusader and opposition politician who organized several large national protests this year, has been barred from running because of a series of criminal cases that he and rights advocates call politically motivated. Yet, even if he were allowed to run, it is doubtful that he would be popular enough to threaten Mr. Putin.
A recent entry into the race, Ksenia Sobchak, a journalist and celebrity reality show host, as well as the daughter of Mr. Putin’s political mentor, is running with what many consider at least the tacit approval of the Kremlin, to divide the opposition vote.
The rest of the field is dominated by novices plugging a particular cause or political war horses like the Communist Party candidate, Gennady Zyuganov, and Vladimir Zhirinovsky, a right-wing nationalist, both septuagenarians who have unsuccessfully contested elections for decades.
The Kremlin does not exactly encourage challengers. Opposition figures get little or no access to national television, and there are countless hurdles to registering as a candidate. To cite just one, independent candidates have to collect hundreds of thousands of signatures of endorsement from members of the public from at least 43 regions of Russia during an abbreviated, three-month campaign.
In 2008, term limits forced Mr. Putin to yield the presidency to a handpicked successor, Dmitri Medvedev, and to slide into the prime minister’s seat. But he assumed his old position in 2012 with a back room maneuver that prompted mass street demonstrations.
Ever since, the Kremlin has set about undermining the independent news media and any civic society organizations or other groups deemed as having the ability to coordinate public demonstrations. Mr. Putin, always quick to blame the West in general and the United States in particular for any problems within Russia, accused Hillary Clinton, then secretary of state, of organizing the street protests.
Once back in the presidency, Mr. Putin set about extending the presidential term to six years. There has been widespread speculation that he might fiddle with the constitution again this time to allow him to run again. Yet, despite his popularity, many analysts said Russians were not inclined to accept a president for life.
Some analysts consider Wednesday’s announcement as marking less the start of the election campaign than the beginning of the struggle within the Kremlin and the Russian elite to succeed Mr. Putin.
The initial reaction from the opposition was to try to laugh off the inevitable. “He wants to stay in power for 21 years,” Mr. Navalny wrote in a tweet, subtracting the years he was prime minister. “In my view, that’s a bit too long. I suggest we don’t agree”
The official line was summed up by Ramzan Kadyrov, the pugnacious ruler of Chechnya, a Russian republic that Mr. Putin has allowed him to turn into something of a private fief.
“It’s only him who is capable of resisting the massive, ruthless and unprecedented attack organized by our frenemies from the U.S. and Western Europe,” Mr. Kadyrov wrote on Instagram.