• Russian leader Vladimir Putin was invoked roughly a dozen times in the 90-minute debate between President Joe Biden and former President Donald Trump.
• The two candidates, who have navigated the White House relationship with the Kremlin for a mandate each, shared opposing views of the Russian leader.
• Putin has seldom commented on the fate of U.S. elections, vowing to "work with any U.S. leader," but fleetingly expressing preference for Biden to assume the top job.

There appeared to be an additional presence on stage with Democratic U.S. President Joe Biden and Republican former President Donald Trump in Thursday night's CNN electoral debate: Vladimir Putin

The Russian leader was invoked roughly a dozen times in the 90-minute volley of verbal blows on domestic and foreign policy between the two candidates. Both have navigated the White House relationship with the Kremlin for a mandate each and shared very different views of the Russian leader.

Trump — who has denied accusations that Moscow interfered in his favor in the 2016 election — claimed that Putin would be deterred from conflict if he respected the leadership of opposing global superpowers.

"As far as Russia and Ukraine, if we had a real president, a president that knew — that was respected by Putin, he would have never — he would have never invaded Ukraine," Trump said, according to a CNN transcript of the debate.

Dubbing Ukrainian leader Volodymyr Zelenskyy as "the greatest salesman ever," Trump again criticized the extent of U.S. financial support for Kyiv throughout the conflict. Two months ago, Washington approved a foreign aid bill that earmarked roughly $60 billion for the war-torn country.

"I will have that war settled between Putin and Zelenskyy as president-elect before I take office on January 20th. I'll have that war settled," Trump said, without disclosing any details.

Trump said, however, that Putin's latest demands for peace negotiations to begin — which include the withdrawal of Kyiv's forces from Ukrainian territories illegally annexed by Russia — are "not acceptable."

In a separate pledge, Trump vowed to ensure the release of Wall Street Journal reporter Evan Gershkovich, who was detained in Russia in March 2023 and now faces trial on charges of espionage.

"I will have him out very quickly, as soon as I take office, before I take office," Trump said, noting that Putin is "probably asking for billions of dollars for the reporter." The Russian leader has previously signaled interest in a potential prisoner swap for Gershkovich, rather than in financial compensation.

Zelenskyy has previously called Trump's claim that he could end the Ukraine war in 24 hours "very dangerous" and appeared apprehensive over a potential White House return of the Republican candidate.

'He wants all of Ukraine'

In keeping with the frosty relations between the Kremlin and his administration, Biden took a more glacial tone when characterizing Putin.

"The fact is that Putin is a war criminal. He's killed thousands and thousands of people. And he has made one thing clear, he wants to re-establish what was part of the Soviet Empire, not just a piece, he wants all of Ukraine," Biden said. In addition to its four illegal annexations since the 2022 invasion, Russia also previously took control of the Crimean Peninsula from Ukraine in 2014.

"Do you think he'll stop there? Do you think he'll stop ... if he takes Ukraine? What do you think happens to Poland? What do you think of Belarus? What do you think happens to those NATO countries?" Biden asked.

The prospect of a potential escalation of the conflict into Europe has long underpinned the NATO military alliance's support of nonmember Ukraine, with Finland and Sweden abandoning their long-standing neutrality to join the coalition. Russia has in turn cited neighboring Ukraine's aspirations to join NATO as a threat to its security and one of the reasons behind its military action.

In response to accusations from Trump that a lack of respect for Biden from leaders such as North Korea's Kim Jong Un, China's Xi Jinping and Putin will lead the U.S. into "World War Three," the current president retorted: "What happens if, in fact, you have Putin continue to go into NATO? … Attack on one is attack on all. You want to start the nuclear war he keeps talking about. Go ahead ... See what happens then."

Biden also took a swing at his opponent's engagement with the Ukraine war, saying Trump "encouraged [Putin]: do whatever you want."  

In 2022, Trump lavished praise on Putin's "genius" invasion strategy on Ukraine, characterizing the Kremlin leader as a "guy who's very savvy" and whom he "knows very, very well," NBC News reported.

CNBC has reached out to the Russian and Ukrainian Ministries of Foreign Affairs. The Kremlin will not comment on the Biden-Trump debate as it is an internal U.S. matter, spokesperson Dmitry Peskov said Friday, according to Reuters.

Putin's preference for Biden?

Putin has seldom commented on the fate of the U.S. elections, vowing to "work with any U.S. leader," but did fleetingly express a preference for Biden to assume the top job.

″[Biden] is more experienced and more predictable. He is an 'old school' politician," he said in February.

Putin has nevertheless repeatedly criticized Washington's stalwart support of Ukraine and lambasted the alleged weaponization of the U.S. judicial system against Trump, who was found guilty on 34 felony charges in late May.

"They [the U.S.] are burning themselves from the inside, their state, their political system," Putin said this month.

Since its 2022 invasion, Ukraine has become the top beneficiary of U.S. foreign aid under the Biden administration, receiving over a hundred billion dollars worth of financial support, weapons and equipment.