From Byron York:

Serhiy Leshchenko is well known in Ukraine as a journalist, crusader against corruption, and a member of Parliament. In August 2016, a few weeks after Trump's statements about Crimea, Leshchenko took on a new task. On Aug. 28, the Financial Times published a story, "Ukraine's leaders campaign against 'pro-Putin' Trump," which began:

For years, Serhiy Leshchenko, a top Ukrainian anti-corruption campaigner, worked to expose kleptocracy under former president Viktor Yanukovich. Now, he is focusing on a new perceived pro-Russian threat to Ukraine: U.S. presidential candidate Donald Trump.
The story went on to recount how Leshchenko, working with Ukraine's anti-corruption bureau, published the "black ledger," which was purported to be a document listing secret cash payments to, among others, Manafort, during the Yanukovych regime. When the New York Times published a front-page story on the ledger: "Secret Ledger in Ukraine Lists Cash for Donald Trump's Campaign Chief," the ensuing controversy forced Manafort to resign.

Leshchenko, speaking from Ukraine, made no secret of his desire to tip the U.S. presidential election. "A Trump presidency would change the pro-Ukrainian agenda in American foreign policy," Leshchenko told the Financial Times. "For me it was important to show not only the corruption aspect, but that [Trump is a] pro-Russian candidate who can break the geopolitical balance in the world."

Some gave Leshchenko and his allies credit for helping shape the U.S. election. "Ukraine's anti-corruption activists have probably saved the Western world," a professor studying Ukraine and Russia told the Financial Times.

The only problem was that the black ledger may or may not have been legitimate. There's no doubt that Manafort received payments from Ukraine. He was convicted on charges of not paying taxes on millions of dollars in income from that country. But there is also no doubt that in all of Manafort's legal proceedings with Trump-Russia special counsel Robert Mueller, the black ledger was never cited as evidence. "It is true that some aspects of the 'black ledger' story remain unclear," the Washington Post wrote recently. "Questions about the origins and authenticity of the documents persist; as Post reporters noted, Mueller's office didn't introduce the ledger at Manafort's trial."

But the ledger was definitive proof of one thing: the determination of Ukraine's political and activist establishment to exert influence over the 2016 U.S. presidential election. The Financial Times article ended with this: "It was a consensus view, Leshchenko suggested to the Financial Times, telling the paper that the majority of Ukraine's politicians 'are on Hillary Clinton's side.'"