Checkmating Vladimir Putin

As a result, only a few police officers guarded St Petersburg8217;s main commercial street, Nevsky Prospekt. And that was where Kasparov and thousands of others 8212; as many as 5,000 by some estimates 8212; poured through a barricade and marched into the city8217;s historic centre, defying the government8217;s ban on the event and the country8217;s recent history of political apathy.

The whole thing lasted only two hours, ending with brief clashes with the police and more than 130 arrests, including those of several opposition leaders, though not Kasparov. Still, it was one of the largest protests against President Vladimir V. Putin8217;s Russia.

And to Kasparov, it was a first crack in the authoritarian political system Putin has created, one that he has committed himself to dismantling as presidential elections approach next March.

Kasparov, 43, is not Putin8217;s only critic, but he may be the most prominent. And he has brought to oppositional politics the same energy that characterised his chess, attacking Putin and the Kremlin with language rarely spoken so bluntly in Russia.

This is not the place Kasparov expected to be when he resigned from the world of professional chess two years ago, quitting while still the highest-ranked player, if no longer the world champion. He is a famous man and a wealthy one, the author of numerous books on chess and its lessons for life, who is now leading acts of civil disobedience in an uphill battle to protest Putin8217;s policies.

Kasparov is the chairman of the United Civil Front, an organisation he formed in 2005 to promote activism in a country where it has steadily disappeared. He is also the guiding strategist behind the Other Russia, a collection of groups from across the political spectrum united by their marginalisation by authorities loyal to Putin.

Kasparov has always been something of an outsider. He is half Jewish and half Armenian, born in Baku, the capital of mostly Muslim Azerbaijan. He moved to Moscow in 1990 when tensions between Armenians and Azeris intensified.

By then he was already world champion, a title he won in 1985 as a brash upstart against Anatoly Karpov, the champion considered a favorite of the Soviet establishment. Kasparov became a strong advocate of glasnost and perestroika, Mikhail S. Gorbachev8217;s policies of opening up the Soviet Union in the 1980s.

When a coup against Gorbachev failed in August 1991, Kasparov threw his support behind Boris N. Yeltsin and the other new democrats. For a time, he was a leader of the Democratic Party of Russia. He broke from Yeltsin to support a challenger, Aleksandr I. Lebed, in the 1996 elections.

One criticism against him has been political fickleness. A constant, however, has been his opposition to Putin. A question that hovers over him is whether he will run against the person who emerges as Putin8217;s chosen successor. He demurs, but does not deny the possibility.

8211;STEVEN LEE MYERS