As head of the largest party in parliament, with 138 seats, he routinely clashes with the Kremlin.
In the past he has had a record of caving in. This time that may be difficult. The severity of Russia's crisis and President Boris Yeltsin's intense unpopularity is increasing pressure on the Communist leadership to harden its stance.
The odds are that Mr Zyuganov will haggle further but settle in the end.
But if the party ultimately votes for Viktor Chernomyrdin as Prime Minister - there are two more ballots to go - the Communists risk alienating the electorate.
Mr Zyuganov also has internal political problems. He heads a combustible coalition of "red-brown" (Communist-nationalist) political forces that contains hard-line elements. Some of them want to extract more concessions. Others are adamantly opposed to anydialogue with the Kremlin.
The pressure from the radical wings, on the right and on the left of his so-called National Patriotic Union, is reaching a new pitch. If he fails to respond, his position as leader, which is already suspect, would become more precarious.
Yesterday, the Communists were demanding - as the price of their co-operation - 10 ministries, including economics and the powerful interior ministry, which controls the police. They are also demanding the resignation of President Yeltsin once a new government is formed.
Although isolated and weak, a cornered Mr Yeltsin is still capable of dissolving the parliament. This would also happen automatically if the Duma throws out Mr Chernomyrdin's nomination three times.
The crisis threatens to destroy a balancing act that Mr Zyuganov, 52, has been engaged in since he took over the party leadership in 1993.
Since then he has succeeded in turning the ruins of the Communist Party of the Soviet Union into the largest political entity in Russia, with 500,000 members.
At his back stands an assorted army of liberal democrats, left-wing nationalists, Slavophile patriots, Marxist-Leninist revivalists, Stalinists, and more. Splits abound over ideology, and between the Communist elite sitting in the Duma, the party apparatus, the regional leaders and the rank and file.
Although the party has a rump of elderly and rural support (average age, 52) its base has been widening. Only one-fifth is made up of blue-collar workers; more than half of the party's support is estimated to be found in the worlds of engineering, technology, culture, science, education and medicine, and among the military.
Mr Zyuganov, podgy in appearance and plodding in manner, glides back and forth across the ideological spectrum. He is the author of A Word to the People, the manifesto of the men behind the failed hardline coup against Mikhail Gorbachev in 1991.
He is an ardent conspiracy theorist, who believes the West is plotting to create a "New World Order". Like many in the Communist camp, he remains silent about Stalin's crimes but enthusiastically praises the dictator's victory over Hitler, and his industrial achievements.
Yet Mr Zyuganov has also espoused a policy of "constructive opposition" and has quietly worked in parliament with Mr Chernomyrdin in the past.
Disaffected radical forces on the left have long accused him of "parliamentary cretinism" as a result. The pressure to stand firm against Mr Yeltsin in the Kremlin's hour of weakness are now stronger than ever.
At the ninth party plenum, in December 1996, Mr Zyuganov argued that co-operation with the government was the "least bad option".
The pragmatism of his party was exposed in April in the row over the confirmation of Sergei Kiriyenko as prime minister.
After rejecting Mr Yeltsin's youthful favourite with great gusto, the Communists and their allies caved in at the third and final vote. Mr Kiriyenko got the job. The Communists looked like fat cats, closer to the boss classes than to the masses. This time it will be much harder for Mr Zyuganov to back down.