Speculation is growing that Vladimir Putin will have to ease his grip on power if he wants to remain Russia's leader. His approval rating, at 80 percent a year ago, has been driven to 60 by, among other things, an uncertain economic future, critics exploiting the Internet's increasing popularity and the slowly maturing disgust among Russians at the prime minister's cynical plan to return to the presidency next year. The usually haughty Putin provided visual symbolism for these changes by appearing shaken last month when boos greeted his appearance at a martial arts fight.