Yesterday, in the halls of Russia's new parliament, he mused confidently on how another military assault by Mr Yeltsin on another large white concrete building might put him and his supporters in power.
"Everything is fluid; everything is changing. The government is shifting; the opposition is changing," said Mr Konstantinov, his mood and cause suddenly lifted by the Kremlin's military adventure in Chechnya.
Along with many other champions of a muscular Russian nationalism, he believes the onslaught on Dzhokhar Dudayev's Presidential Palace in Grozny is reviving the very forces Mr Yeltsin thought he had obliterated when he destroyed the old Soviet-era legislature.
Though himself no longer a deputy - he was in jail when elections were held in December 1993 - Mr Konstantinov spends much time in the State Duma, plotting strategy with other colleagues in the disbanded National Salvation Front, a hardline umbrella group that Mr Yeltsin once targeted as a principal threat to Russia's fledgling democracy.
"The situation in Chechnya is a fault line along which a new political re-grouping is taking place, along which new forces are emerging," said Mr Konstantinov. " It is hard to say what the political scene will look like by spring but it will be very different from what we are used to."
While Mr Yeltsin's former liberal allies, men like the former prime minister, Yegor Gaidar, wring their hands in despair at the military debacle in Chechnya, the President's enemies are rubbing their hands with glee. They condemn the bloodshed in Chechnya but it is political calculation as much as their consciences that animates their anger.
One of Mr Yeltsin's few cheerleaders is Vladimir Zhirinovsky. "What if an American division entered the city of Dallas in Texas, and someone dared open fire at that division. What would Clinton do? He would destroy anyone who would dare take up arms against the US army," the Liberal Democratic Party leader told the State Duma.
Mr Gaidar and his Russia's Choice party had hoped that Mr Yeltsin's political isolation might allow them to put a brake on the military campaign through action in parliament. Yesterday, they succeeded in passing a non-binding resolution calling on Mr Yeltsin to stop the war but failed to pass other, more concrete motions that went beyond mere appeals.
A session which liberals had seen as the best hope of stopping the war often lapsed into near farce. Mr Zhirinovsky provided further disruption by furiously rejecting an attempt by a lawyer to serve a summons demanding that he appear in court for defaming the head of the Counter-Intelligence Service.
Deputies then debated whether Russia was being undermined by a "fifth column". A resolution calling for a witch-hunt failed but still got the support of nearly half the 300 legislators. Another motion, also voted down, demanded that Mr Zhirinovsky and Anatoly Lukyanov, the chairman of Mikhail Gorbachev's Congress of People's Deputies, be given seats on Russia's Security Council, the Kremlin's main decision-making body.
It is such confusion that gives Mr Konstantinov and other belligerent nationalists comfort - and deeply disturbs Russia's liberals. "What awaits Russia after the war in Chechnya?" asked Izvestia newspaper yesterday in a headline over an article by Emil Pain, a member of Mr Yeltsin's presidential council, who warned of mounting xenophobia.
"Even those outraged by war see little benefit in making common cause with what they see as an increasingly marginal and politically feeble liberal cause," he lamented.