JOHN YANG: Welcome to the "News Hour."

We begin tonight with a political earthquake in Ukraine.

President Volodymyr Zelenskyy's chief of staff, Andriy Yermak, the country's second most powerful person, has been forced to resign amid a corruption scandal.

This comes as Ukraine is enmeshed in negotiations with the Trump administration on a possible end to Russia's war on Ukraine.

Special correspondent Jack Hewson is in Kyiv.

Jack, who is this chief of staff and why is this such a big deal?

JACK HEWSON: Well, John, Andriy Yermak, as you mentioned, was President Zelenskyy's chief of staff and essentially the second most powerful man in the country.

Zelenskyy came to power on the back of a landslide election in 2019 and, with that authority, centralized power around the president's office.

And Yermak was a very big part of that.

Officially, Ukraine is a hybrid, premier-presidential system.

But under Zelenskyy and Yermak, it's taken on a much more of a top-down executive-dominated shape.

And under wartime powers, which include martial law and the freezing of any presidential or parliamentary elections, that's centralized even more.

And as one anti-corruption activist put it to me earlier this evening, Zelenskyy is the face of government, while Yermak was the brains.

So for Yermak to be gone is huge.

JOHN YANG: Corruption.

There is an embezzlement scandal that's enmeshing many high-ranking officials in Zelenskyy's circle.

Tell us about that.

JACK HEWSON: Well, the scandal is about an investigation by the anti-corruption authorities called Operation Midas, which has resulted in a string of high-level raids and charges over the last month.

There have been a laundry list of high-ranking Cabinet officials, including a former deputy prime minister, who have either been charged or named.

The cornerstone figure in all of this is a man named Timur Mindich.

He's the former business partner of Zelenskyy, with whom he set up a media company before he was president.

And Mindich and his broader group of appointees and ministers are accused of embezzling $100 million worth of public money that was supposed to be spent on the energy sector.

Instead, it was embezzled allegedly through inflating infrastructure procurement contracts and siphoning off funds.

So, right now, with Ukraine under daily bombardment by Russian drones and missiles, which are blowing up electricity stations and substations, causing blackouts, as you can imagine, Ukrainians are absolutely furious that, at this time of suffering, these Cabinet ministers have allegedly been stealing public money that should have been spent on fixing this electricity grid, instead of enriching themselves.

Authorities have not yet confirmed if the raid is related to Operation Midas, but following his raid, Yermak has gone ahead and resigned nonetheless.

JOHN YANG: How is all this or how might all this affect efforts to end the war?

JACK HEWSON: Well, essentially, this weakens the Ukrainian negotiating position.

It allows the Kremlin to paint Ukraine as a corrupt and unreliable partner to its allies.

It allows Putin to draw an equivalent between Ukraine and far more corrupt or dictatorial regimes, and it throws the peace negotiation into temporary disarray, as Yermak was also Zelenskyy's lead negotiator.

But it's also bad for Ukraine's image with its allies.

One major criteria for Ukrainian aid has been to eradicate corruption in this country, and this scandal proves very clearly that that's not what's happened.

And at this point -- and this is a point that President Zelenskyy himself made tonight in his evening address announcing the departure of his most valued aide.

VOLODYMYR ZELENSKYY, Ukrainian President (through translator): To preserve our internal strength, there must be no reasons to be distracted at anything else except for defense of Ukraine.

I don't want anybody to be questioning Ukraine, and that's why we have today's decisions.

JACK HEWSON: And many perceive this weakened position that Ukraine now finds itself in as a complicating factor in why the Trump administration is able to push hard for a peace deal on terms that many perceive to be too favorable to Russia -- John.

JOHN YANG: Special correspondent Jack Hewson in Kyiv, thank you very much.