KYIV - How long can he keep it going?

Night after night, Ukrainian President Volodymyr Zelenskiy delivers rousing video addresses, rallying his troops in their fight against the Russian invaders and trying to keep the world's attention focused on his nation's plight.

He has successfully lobbied the West for arms, lifting taboo after taboo in the process -- initially on the West sending lethal aid of any kind and more recently on Western deliveries of battle tanks that may help Ukraine mount a counter-offensive.

Zelenskiy, now 45 and in power since 2019, shows no sign of letting up.

Nor does Russian President Vladimir Putin, who launched his "special military operation" in Ukraine on Feb. 24, 2022 and appears to be preparing for a long war.

When Russian troops poured over the border, few predicted the transformation in Zelenskiy, a former TV comedian whose trust ratings had been waning as public anger rose over widespread corruption, economic malaise and bad governance.

In the buildup, as Russia massed forces on his borders, he had criticised foreign embassies and companies for leaving Ukraine, saying they were hurting the economy and - in public at least - appeared to play down the threat of a major invasion.

He is now a household name around the world, a symbol of Ukrainian resistance. In Ukraine, his popularity ratings have almost tripled and are unusually stable.

Easy-going and relaxed when meeting newcomers in his heavily fortified headquarters, dressed in military khaki whether meeting royalty or visiting soldiers near the frontline, Zelenskiy projects an image of steadiness and steadfastness.

He has huge milestones still to clear. He is yet to secure supplies of the sophisticated Western fighter jets he says are needed to push back Russian troops, or promises of fast-track membership to the European Union. Joining the NATO military alliance still looks out of reach.

But though sometimes puffy-faced, with lines under his eyes, there is no indication he is running out of steam, and last month he launched a government shake-up to quash a public outcry over a corruption scandal.

"Zelenskiy surprised many people ... They underestimated his leadership qualities," said Volodymyr Fesenko, a Kyiv-based analyst who said Putin misjudged Zelenskiy.

"(Putin) prepared a special operation not a full-fledged war ... because he thought Zelenskiy and the Ukrainian army were weak and that they would not be able to put up lengthy resistance. This proved to be a mistake."

'YA TUT'

As Ukraine's fate hung in the balance at the start of the Russian invasion, Zelenskiy filmed himself on a mobile phone to declare that he and his country would fight on.

"Ya tut," he said, meaning: "I am here."

It was the start of a social media blitz that he has sustained throughout the war, delivering a simple message: "We will win."

Reuters reporters saw Ukrainian soldiers cry in a dugout near the war front as he delivered a rousing New Year's address.

"This is the year when Ukraine changed the world. And the world discovered Ukraine. We were told to surrender. We chose a counterattack!" Zelenskiy said.

By contrast, Putin often seems glum and isolated, issuing threats to the West or Ukraine from the Kremlin and rarely seen in public except at choreographed events.

A steady stream of foreign leaders, dignitaries and celebrities have made the long train journey to Kyiv to meet Zelenskiy in the presidential headquarters overlooking Kyiv. Billions of dollars in foreign aid has poured in.

Aides describe an over-full schedule that since the day of the invasion has included 377 phone calls with other leaders and heads of international organisation, 41 addresses to parliaments and foreign publics, and 152 meetings and scores of other addresses.

'NOW IS NOT THE TIME'

A Russian-speaking Ukrainian from a Jewish family in the steel-making city of Kryvy Rih, Zelenskiy began his career as an actor.

He gained prominence playing the main role in the television series "Servant of the People", which struck a chord with Ukrainians fed up with the corruption.

In it, he plays an honest schoolteacher who gains fame after a classroom rant about corruption goes viral online and becomes president, going on to outwit crooked lawmakers and businessmen.

Then in 2019, life imitated art. Zelenskiy was elected president after pledging to fight corruption during a campaign that relied on quirky social media posts in a foretaste of his powerful online outreach during the war.

In a video recorded soon after Russia's invasion, he cited intelligence saying Moscow had declared him target number one and that his family - his wife Olena Zelenska and their two children - was target number two.

Anton Grushetsky, deputy director of the Kyiv International Institute of Sociology, put public trust in Zelenskiy at 70% to 80%.

"The stability of this trust level is unprecedented in Ukrainian history," he said.

His main rivals have been largely frozen out of decision-making, and some foreign diplomats say privately that they are uneasy about the concentration of power in his team's hands.

The political truce has held and Zelenskiy has been able to launch a campaign to weed out officials suspected of corruption, including some close to his own power base.

Former President Petro Poroshenko, whom Zelenskiy defeated in the 2019 election, said giving an assessment of Zelenskiy's wartime performance would be inappropriate during the conflict.

"Since Feb. 24, 2022, I am not the leader of the opposition, because both Zelenskiy and Poroshenko are soldiers. And all Ukrainians should unite not around personalities, but around Ukraine," Poroshenko told Reuters.

"The people will give any assessment of the work of Zelenskiy and Poroshenko after our victory."

For now, he appears to have the people's support. "He stayed here, he didn't panic," said Anton Fedorenko, a unit commander code named Mazda serving in eastern Ukraine.

"He immediately launched a series of actions and deeds. He drew public attention to Ukraine, which is also very important. He brought this problem to the world."

(Editing by Timothy Heritage)