The Union of Right Forces began directly criticizing President Vladimir Putin for the first time this fall after learning that the Kremlin would break a promise to deliver seats in the next State Duma, a senior party official said.

"At first, Kremlin spin doctors said the party would be allowed into the Duma if it refrained from criticism, but then they changed their minds and decided not to keep their promise," said the official, who asked for anonymity for fear of reprisal from both the party and the Kremlin.

"The party is angry, and now the only chance it has to get into the parliament is to gather the protest vote," the official said. "This is why SPS's stance has radically changed."

Communist and Yabloko officials said their parties had also been promised Duma seats if they promised not to criticize Putin. All the officials would only speak on condition of anonymity.

A Kremlin spokesman said backroom deals had not taken place with any party.

The Union of Right Forces, or SPS, has long been viewed as pro-Putin because of its tacit support of Kremlin policies. All that has changed in recent weeks. SPS has produced a critical television commercial and, in a sharp reversal, joined The Other Russia opposition coalition for a Dissenters' March. For their part, Putin and state television have offered sharp criticism of SPS.

Speaking about SPS's previous support of Putin during a televised debate earlier this month, party leader Nikita Belykh said simply: "We were wrong."

Analysts said the Kremlin might have ditched SPS because it threatened to take votes from United Russia, which is facing an uphill battle in its goal to win by a landslide Sunday.

The senior SPS official said the party kicked off its Duma campaign in September with no plans to court voters actively. "They thought it was useless and started behaving like puppets in the hands of the Kremlin," the official said.

A regional party official complained to a reporter on the sidelines of SPS's pre-election convention in September that the party had bowed to Kremlin pressure by not including independent Duma Deputy Vladimir Ryzhkov on its list of candidates.

In the following weeks, the lines between SPS and United Russia gradually blurred in voters' minds, and SPS realized that the Kremlin would not help it clear the 7 percent threshold to get into the Duma, the SPS official said.

"In the middle of the campaign, Kremlin spin doctors changed their minds, and we understood that we had been sidelined," he said.

The first public indication of strained relations between SPS and the Kremlin surfaced shortly before the SPS convention, when Putin suggested during an annual meeting with foreign analysts and journalists that party co-founder Anatoly Chubais might use his position as the head of Unified Energy System to bankroll SPS. After the jab, Chubais was noticeably absent from the convention.

Putin rebuked liberal parties like SPS at an event organized by the For Putin movement last week. "They want to come back, to return to power, to spheres of influence, and gradually restore oligarchic rule based on corruption and lies," he said.

State television appears to only mention SPS in critical reports these days, unlike the Communists and Yabloko, whose activities tend to be portrayed in a neutral way. On Sunday, Rossia's "Vesti Nedeli" program broadcast an interview with Mikhail Barshchevsky, Putin's representative in the Constitutional Court, who criticized SPS and said its acronym meant sovsem plokhaya situatsia, or a really bad situation.

Several women from the Krasnodar region told the same program that SPS had failed to pay them for distributing campaign leaflets. "How can a party that doesn't pay its workers be allowed into the Duma?" one woman said.

Police across the country have confiscated millions of SPS newspapers in recent weeks, citing various purported legal violations.

In response, SPS took part in The Other Russia-led Dissenters' Marches over the weekend in Moscow and St. Petersburg, after earlier refusing to associate itself with the outspoken, anti-Putin coalition led by former chess champion Garry Kasparov. Kasparov and SPS co-founder Boris Nemtsov were among those detained by police -- Kasparov in Moscow, Nemtsov in St. Petersburg -- during the demonstrations.

Police detained six SPS activists Tuesday for staging an unsanctioned protest, in which they tried to deliver a giant plastic razor to Central Elections Commission chief Vladimir Churov at the commission's Moscow headquarters, party official Sergei Gorodilin said.

In a television interview in May, Churov swore on his beard that the Duma elections would be fair.

SPS has also orchestrated a series of moves against Putin. Last week, it asked the Supreme Court to remove Putin from United Russia's candidate list, saying he had abused his office to campaign for the party. The request was rejected.

SPS even produced a campaign commercial accusing Putin of wanting to return the country to the Soviet Union. "On Dec. 2, the destiny of Russia will be decided for many years to come," a voice-over says on the commercial. "We are told that there will be a referendum of trust for President Putin. But in reality, it will be a referendum to bring us back to the Soviet Union."

The commercial was broadcast on Channel One. But the Central Elections Commission decided Thursday that it broke campaigning rules and ordered it off the air.

SPS decided Friday to pick Nemtsov as its candidate to challenge Putin's preferred successor in the presidential election next year.

No party running for Duma seats has been as critical as SPS in this campaign.

"You cannot trust the Kremlin. They cheat people," said Anton Bakov, an independent Duma deputy who is in charge of SPS's election strategy.

Bakov denied that any deal had been reached for the Kremlin's support. "But they said they wouldn't hamper us during the election campaign," he said.

Nemtsov also denied that the party had relied on the Kremlin. "We have never placed our hopes on the Kremlin. They have opposed us with all the means at their disposal," he said.

"We are against Putin's Plan and where he is taking our country. This is why we are the opposition," Nemtsov said.

In the 2003 Duma elections, SPS took a starkly different stance, with party leaders saying they could not play the opposition card because that would mean opposing reforms that they backed.

Communist, Yabloko and SPS officials said the Kremlin had played an active role in this fall's campaign. Opposition leaders have been asked to meet regularly with Vladislav Surkov, the powerful deputy head of the presidential administration who coordinates the Kremlin's relations with the parties, to review their strategies, the officials said.

"[Communist leader Gennady] Zyuganov is not interested in being in the opposition. He only wants a Duma seat with a faction of his own," a senior Communist official said.

In return for this, he said, the Communists were asked not to criticize Putin during the campaign and, after Putin agreed to be a United Russia candidate, not to criticize United Russia.

Sergei Reshulsky, a Duma deputy and senior Communist member, denied that the Communists had an agreement with the Kremlin. "If we did, the Communists would have disappeared from the political scene by now," he said.

A Yabloko Duma candidate said party leader Grigory Yavlinsky had rejected a Kremlin offer for Duma seats.

Sergei Mitrokhin, a senior Yabloko official, denied that there had been any such offer.

Kremlin spokesman Dmitry Peskov said the Duma's makeup would be decided by voters, not by Kremlin deals. "It is not up to the Kremlin to decide who gets into the Duma, but the results of the elections," Peskov said. "Surkov is only engaged in matters of internal politics."