MOSCOW  For a few days this month, Moscow political circles were transfixed by a rather exotic spectacle: the leader of an opposition party was criticizing Prime Minister Vladimir V. Putin.

This was not just any leader. It was Sergei M. Mironov, whose career in the opposition has been distinguished by passionate loyalty to Mr. Putin. When he ran against Mr. Putin for president in 2004, he said he was running because “when a leader you believe in goes into battle, you can’t leave him alone, you must stand with him.” Two years later he promised that A Just Russia, his new party, would “follow the course of President Vladimir Putin and will not allow anyone to veer from it after Putin leaves his post.”

Many observers long ago wrote off A Just Russia as “pocket opposition,” devised to give the appearance of political competition where none existed. So it came as a surprise when Mr. Mironov, who Mr. Putin installed as speaker of the upper house of Parliament, told the television talk show host Vladimir V. Pozner that it was “outdated information to say that we, and personally I, have supported Vladimir Putin in everything,” noting that the party members “categorically opposed” Mr. Putin’s budget. Mr. Pozner was taken aback  “nobody in that position has said anything negative about Putin,” he said later  and watched with real curiosity to see if officials at state-controlled Channel One would edit out the remark before it was broadcast in Moscow. They did not.

For six strange days, Mr. Mironov defended his right to criticize Mr. Putin while officials at the governing party, United Russia, said he should lose his post for his show of ingratitude. The fuss ended with a public reconciliation between the pro-Putin parties, and all the planets seemed to realign. But during an unpredictable political season in Russia, a question was left hanging in the air: Under the right set of circumstances, could a docile, dependent opposition turn into the real thing?