The world has an abiding image of Garry Kasparov. It is that of the plucky chess grandmaster who took on Anatoly Karpov in a marathon contest and won, becoming the youngest ever world chess champion at the age of 22.
He was the challenger, the scrappy anti-government contestant engaged in a battle of the titans against the champion who had the favour of the Soviet establishment. Twenty-two years on, his hair now streaked with grey, Mr Kasparov is again the upstart, challenging the powers that be. He was chosen at the weekend as the candidate of the Other Russia opposition alliance, aiming to succeed Vladimir Putin as president.
It would be tempting to describe the forthcoming political battle as the biggest championship match of Mr Kasparov's life. But he knows it is not. Why would Russians elect to the presidency a man born in Azerbaijan to a Jewish father and an Armenian mother? The fact is, they won't. As the whole of Russia knows, in the climate of government-controlled politics prevalent in the country, Mr Putin – constitutionally barred from serving for a third term as head of state – will be succeeded by the candidate of his choice.
"The goal of the Other Russia is not winning elections, but to have an election," said Mr Kasparov after he beat five other candidates to run as the presidential contender of the Other Russia, a loose coalition grouping. "We're trying to force the regime to accept our rights to participate in free and fair elections, to agitate the Russian population and Russian public to support our ideas."
But taking on the system in Russia is a risky business, as other opponents of Mr Putin have found. Criticising the president and his acolytes can mean physical harm, forced hospitalisation or even death, which came suddenly for Mr Putin's prominent critics Anna Politkovskaya and Alexander Litvinenko. Mikhail Kasyanov, a former prime minister sacked by Mr Putin who decided to run for the presidency, has been accused of corruption. Like Mr Kasparov, he has all but disappeared from state-run television.
Risk-taking has been second nature to Mr Kasparov – who is protected by bodyguards when in Moscow – for as long as he has played chess. In the days of the Soviet Union, chess was a national obsession, with enthusiasts setting out their boards in parks. His talent for the game became clear at the age of five, in his native Baku, where his father, Kim Weinstein, taught him chess moves. Following his father's death from cancer, when Mr Kasparov was seven, he trained at an academy run by the former world champion, Mikhail Botvinnik, and at the age of 12 had won the Azerbaijan championship. The same year, he adopted his mother's Armenian surname, Kasparyan, but changed it to the Russian-sounding version of Kasparov. He became Soviet champion at the age of 18, after winning the world junior championship the previous year.
But the match that brought Mr Kasparov's genius to the attention of a broader public was the chess world championship, pitting him against Mr Karpov, that began in September 1984 in Moscow's Hall of Columns. It was stopped after 48 games – the following February – by the Soviet chess federation, which claimed that both players were exhausted, just as Mr Kasparov was about to win against the champion who was 12 years older. Such a decision to abandon play was unprecedented in the game.
Asked by The Boston Globe last weekend whether this was where his battle with the Russian authorities began, he replied: "Yes. I started by fighting the chess federation and wound up fighting the Soviet regime."
When the rematch finally took place in Moscow six months later, Mr Kasparov won the title. In 1996, he was the first world champion to win against Deep Blue, the IBM computer, as chess marched into the electronic era.
But the world's greatest chess player was losing his edge, despite remaining world number one between 1998 and 2003. In 2000, he lost to the Russian grandmaster, Vladimir Kramnik, after which, he confessed recently to The New Yorker's editor David Remnick, "it wasn't easy to contemplate coming back". "I spent two years trying to recover my position, studying playing ... I never lost my desire, but I really need to be at a cutting edge," he said.
In 2005, after losing to Veselin Topalov of Bulgaria, he left competitive chess for politics. He formed the United Civil Front to "work to preserve electoral democracy in Russia".
Like many born in the Soviet era, Mr Kasparov owed his first taste of " real" politics to President Mikhail Gorbachev and his "glasnost" policies of the late 1980s. But the greater openness also revived festering ethnic wounds in the Soviet republics, along with long-suppressed dreams of independence from the Kremlin, and in Baku, Mr Kasparov had a ringside seat. For Armenia at that time decided to re-stake its claim to the Armenian-dominated enclave of Nagorno-Karabakh, which during the Soviet period had been an autonomous region within Azerbaijan.
As the conflict spread, the Armenian community in the Azerbaijani oil city of Sumgait, on the Caspian Sea, became the target of pogroms in 1988. In 1990, Baku was virtually emptied of its Armenian population after Soviet troops were ordered to the city to put down a separatist insurrection by Azeri nationalists. Mr Kasparov left for Moscow, on a chartered plane with 60 friends and relatives, to become one of the richest refugees fleeing the conflict, and has never returned. He has accused Mr Gorbachev of failing to stop the bloodshed as a warning to the independence-seeking Soviet republics.
With the collapse of the Soviet Union, Mr Kasparov told The Boston Globe, "in 1990 and 1991, I thought the game was over for communism and Soviet-style dictatorship. I didn't plan to become a leader of opposition to the new regime. But when I recognised dictatorship was coming back, I gradually came to the conclusion that I had no choice."
So for the past few months, Mr Kasparov has been manning the barricades, or at least trying to, by launching the "marches of the dissenters" to challenge Mr Putin's supremacy. But the demonstrations by the Other Russia coalition, which includes a motley range of activists from skinheads and nationalists to human rights campaigners and leftists, have been fiercely suppressed.
Marches in Moscow and St Petersburg earlier this year were banned. In April, Mr Kasparov and about 170 supporters were arrested during a demonstration by about 5,000 people in central Moscow, where 9,000 police were on hand. The following month, he and a group of activists were stopped at a Moscow airport and prevented from travelling to southern Russia to hold an officially approved march coinciding with the Russia-EU summit in Samara. Mr Kasparov says Mr Putin's Russia is a "police state". The Russian President was a "brutal dictator" who has "abolished the nature of democratic institutions", he said. "They arrest people everywhere because they are scared stiff."
In July, a member of Mr Kasparov's Murmansk branch, Larisa Arap, was forcibly interned in a psychiatric hospital, in a throwback to a Soviet-era practice, after publishing an article on conditions in children's wards.
Mr Kasparov and his followers also have to contend with officially sanctioned political movements, such as the pro-Putin Nashi youth group, which field hecklers at the opposition marches. Mr Kasparov has shunned foreign funding to head off accusations from Nashi and others that his party is a tool of the US State Department, and has strongly denied he received financing from Boris Berezovsky, Mr Putin's sworn enemy who is exiled in London.
At the alliance's national congress on Sunday, Mr Kasparov received 379 out of the 498 votes cast. Following his selection, he pledged to work for a "democratic and just Russia", and urged the coalition to remain united. So is Mr Kasparov brave, or foolhardy, to take on the Putin machine? Probably both.
But he is entering the fray with his eyes open. He acknowledges that there is "zero" chance of being able to register as presidential candidate because of the technical obstacles on the way, including a requirement of two million signatures in support. The bottom line, according to Mr Kasparov, is that only the Kremlin-approved candidates will overcome the hurdles and be allowed onto the "sacred territory" of national television.
Asked by Mr Remnick whether he feared for his life, Mr Kasparov responded: "I do. The only thing I can try to do is reduce my risk." He does not eat or drink in unfamiliar places, and does not take long-haul flights. He added: "It doesn't help in the end if they really decide to go after you. But, if they did, it would be really messy.
"There would be a huge risk for the Kremlin if anything happens to me, God forbid, because the blood would be on Putin's hands. It's not that they have an allergy to blood, but it creates a bad image, or makes it worse than it already is."
Despite the risks, Mr Kasparov will not relinquish his latest challenge. As a child in Baku, he kept a slogan pinned on his wall. It read: "If not you, who else?"