The arrest of the richest man in any country is always an earthshaking event, and the jailing of Mr. Mikhail Khodorkovsky, the premier among Russia's oligarchs, is no exception. There are a number of explanations for Mr. Khodorkovsky's arrest, but there is no mistaking the chief beneficiary of the move: President Vladimir Putin, who eliminates yet another critic and one more obstacle to his consolidation of political power. And even though a majority of Russians may support the arrest, it is Russian democracy that suffers the most.

Mr. Khodorkovsky, who is worth an estimated $8 billion, was arrested last weekend -- on charges of fraud, tax evasion and forgery -- as his private jet was refueling in Siberia. If convicted, he could be sentenced to 10 years in jail and all his wealth, including his control of the Yukos oil concern, could be seized.

Some would say that the writing was on the wall last summer, when Mr. Platon Lebedev, a key partner of Mr. Khodorkovsky, was jailed on charges of fraud and embezzlement. The arrest was thought to be a warning to Mr. Khodorkovsky from the Kremlin, which wanted to dissuade him from selling part of Yukos to an American company, as well as halt his funding of political opposition parties. Yukos this month completed arrangements for its merger with Sibneft, another Russian oil company, which will create the world's fourth-largest oil company.