The polls, conducted by two of Russia's most venerable public opinion services, indicate that Vladimir Putin's United Russia party (UR) has won less than half the votes. It would mark the party's first failure to top 50 percent in a national election since its creation a decade ago to provide a legislative backstop for then-President Putin's ambitious plans to remake Russia.
In the last Duma elections, in 2007, United Russia won 64 percent of the popular vote, giving it a two-thirds supermajority in the Duma, which enabled it to ram through any legislation it wished and even change the Constitution.
But according to one exit poll conducted by the independent, Moscow-based Public Opinion Foundation, UR saw its support slip by 18 points to just 46 percent on Sunday. A similar poll by the state-funded Russian Public Opinion Research Center (VTsIOM) put UR's support at 48.5 percent.
The fact that the polls were reported by state-owned news agencies suggests that Russian authorities may be resigned to the loss of a pro-Kremlin Duma majority.
Most public opinion surveys in recent weeks have indicated a sharp erosion of support for UR -- though not on such a scale -- and many experts connect that trend to weariness with the authorities and lack of enthusiasm for Mr. Putin's personal decision to run again for president, on the UR ticket, in elections slated for next March.
The same exit polls show substantial gains for the opposition Communist Party, which appears to have boosted its support from around 12 to 20 percent, and the left-wing A Just Russia party, which surged from 8 to around 12 percent. The ultranationalist party of Vladimir Zhirinovsky also appears to have gained a few points, to about 12 percent.
Some experts warn that the official count will only be finished sometime on Monday, and it might differ from exit poll results for a variety of reasons. These include the tendency of exit pollers to disproportionately query urban voters, who tend to be more restive than voters in the remote and hard-to-reach deep provinces, where people tend to be far more conservative and obedient to authority.
Russia's complicated electoral system also provides that votes given to parties that fail to hurdle the 7 percent barrier needed to enter the Duma, as well as spoiled ballots, will be divided up among the winners according to a pro-rated formula that would benefit UR. Hence, experts say, a result of 46 percent for UR could transform into a narrow majority in the 450-seat Duma.
In snow-swept Davlekanovo, an impoverished agro-industrial town about 1,000 miles east of Moscow, local observers noted that Communist Party voters appeared more numerous than in the past, but in early counting more than half the votes were going to United Russia.
"I like Putin, he's a man who gets things done," said Yelena Kuzmina, a social worker, after voting Sunday. "So, I supported United Russia, because it's the party of Putin."