On a leafy side street off Independence Square in Kiev is an office used for years by Donald J. Trump’s campaign chairman, Paul Manafort, when he consulted for Ukraine’s ruling political party. His furniture and personal items were still there as recently as May.
And Mr. Manafort’s presence remains elsewhere here in the capital, where government investigators examining secret records have found his name, as well as companies he sought business with, as they try to untangle a corrupt network they say was used to loot Ukrainian assets and influence elections during the administration of Mr. Manafort’s main client, former President Viktor F. Yanukovych.
Handwritten ledgers show $12.7 million in undisclosed cash payments designated for Mr. Manafort from Mr. Yanukovych’s pro-Russian political party from 2007 to 2012, according to Ukraine’s newly formed National Anti-Corruption Bureau. Investigators assert that the disbursements were part of an illegal off-the-books system whose recipients also included election officials.
Mr. Manafort’s involvement with moneyed interests in Russia and Ukraine had previously come to light. But as American relationships there become a rising issue in the presidential campaign — from Mr. Trump’s favorable statements about Mr. Putin and his annexation of Crimea to the suspected Russian hacking of Democrats’ emails — an examination of Mr. Manafort’s activities offers new details of how he mixed politics and business out of public view and benefited from powerful interests now under scrutiny by the new government in Kiev.
The developments in Ukraine underscore the risky nature of the international consulting that has been a staple of Mr. Manafort’s business since the 1980s, when he went to work for the Philippine dictator Ferdinand Marcos. Before joining Mr. Trump’s campaign this spring, Mr. Manafort’s most prominent recent client was Mr. Yanukovych, who — like Mr. Marcos — was deposed in a popular uprising.
Before he fled to Russia two years ago, Mr. Yanukovych and his Party of Regions relied heavily on the advice of Mr. Manafort and his firm, who helped them win several elections. During that period, Mr. Manafort never registered as a foreign agent with the United States Justice Department — as required of those seeking to influence American policy on behalf of foreign clients — although one of his subcontractors did.
But he also worked to burnish his client’s image in the West and helped Mr. Yanukovych’s administration draft a report defending its prosecution of his chief rival, Yulia V. Tymoshenko, in 2012.
The papers, known in Ukraine as the “black ledger,” are a chicken-scratch of Cyrillic covering about 400 pages taken from books once kept in a third-floor room in the former Party of Regions headquarters on Lipskaya Street in Kiev.
The National Anti-Corruption Bureau, which obtained the ledger, said in a statement that Mr. Manafort’s name appeared 22 times in the documents over five years, with payments totaling $12.7 million.
“Paul Manafort is among those names on the list of so-called ‘black accounts of the Party of Regions,’ which the detectives of the National Anti-Corruption Bureau of Ukraine are investigating,” the statement said.
While working in Ukraine, Mr. Manafort had also positioned himself to profit from business deals that benefited from connections he had gained through his political consulting. One of them, according to court filings, involved a network of offshore companies that government investigators and independent journalists in Ukraine have said was used to launder public money and assets purportedly stolen by cronies of the government.
The role of the offshore companies in business dealings involving Mr. Manafort came to light because of court filings in the Cayman Islands and in a federal court in Virginia related to an investment fund, Pericles Emerging Markets. Mr. Manafort and several partners started the fund in 2007, and its major backer was Mr. Deripaska, the Russian mogul, to whom the State Department has refused to issue a visa, apparently because of allegations linking him to Russian organized crime, a charge he has denied.
Mr. Manafort continued working in Ukraine after the demise of Mr. Yanukovych’s government, helping allies of the ousted president and others form a political bloc that opposed the new pro-Western administration. Some of his aides were in Ukraine as recently as this year, and Ukrainian company records give no indication that Mr. Manafort has formally dissolved the local branch of his company, Davis Manafort International, directed by a longtime assistant, Konstantin V. Kilimnik.
At Mr. Manafort’s old office on Sofiivska Street, new tenants said they had discovered several curiosities apparently left behind, including a knee X-ray signed by Mr. Yanukovych, possibly referring to tennis matches played between Mr. Manafort and Mr. Yanukovych, who had spoken publicly of a knee ailment affecting his game.