Around last November’s election, Paul Manafort, President Donald Trump’s former campaign chairman, resurfaced as a priority for the AP’s Washington investigative team when it became clear he was a leading focus of the government’s inquiry into whether Trump’s campaign had coordinated with Russians to meddle in the presidential election.

Jeff Horwitz and Chad Day, along with AP colleagues in Washington and elsewhere, dove in and after weeks of reporting, learned that Manafort had worked for a Russian billionaire a decade ago and had proposed to him a plan to greatly benefit President Vladimir Putin’s government, even as U.S.-Russia relations under then-President George W. Bush grew worse.

For their exclusive, Horwitz and Day win the Beat of the Week.

Horwitz and Day were already plenty familiar with Manafort, a Republican operative in Washington for decades who veered onto their radar screens when he took over running Trump’s presidential campaign in March 2016. Manafort's previous work as an international political consultant was well known, including work on behalf of former Ukrainian President Viktor F. Yanukovych, who was driven from power in 2014.

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Paul Manafort, Donald Trump's campaign chairman, stands between the Republican presidential candidate and Trump's daughter Ivanka during a walk-through at the Republican National Convention in Cleveland, July 21, 2016.

AP PHOTO / EVAN VUCCI

By August, after extensive reporting across two continents, Horwitz and Day had produced two exclusive stories, including one showing that Manafort had orchestrated a covert Washington lobbying operation until 2014 on behalf of Ukraine's pro-Russia, ruling political party and never disclosed his work as a foreign agent to the Justice Department, as required.

That coverage earned them a Beat of the Week, and Manafort resigned under pressure by Trump suddenly the next day.

After Manafort’s name resurfaced this year as a focus of the government’s inquiring into Russian election meddling, Horwitz and Day circled back to existing sources and reached out to new ones. Weeks passed with little to show for the effort, which kept Horwitz and Day working late into evenings.

The breakthrough: AP obtained Manafort’s confidential business records. He had secretly worked for a Russian billionaire and had proposed a plan to benefit Putin's government.

Then the breakthrough: AP obtained Manafort’s confidential business records, including strategy memoranda and records showing millions of dollars of international wire transfers. The documents, authenticated in interviews with people familiar with Manafort’s business dealings and in other ways, showed that Manafort had secretly worked for a Russian billionaire, Oleg Deripaska, a decade ago and had proposed to him the plan to benefit Putin's government.

The story played widely in print and online and was No. 1 for the week on AP Mobile – a week that also included the health care bill’s withdrawal and other major news.

White House spokesman Sean Spicer, acknowledging AP’s story “has started to catch a lot of buzz,” said Trump was unaware of Manafort’s relationship with Deripaska. "The president was not aware of Paul's clients from the last decade," Spicer said. "What else don't we know? I mean, where he went to school, what grades he got, who he played with in the sandbox?"

Members of Congress said the AP’s revelations guaranteed Manafort will be questioned by committees investigating Russian meddling in the election. “This is not a drip, drip, drip,” said Rep. Jackie Speier, D-Calif. "This is now dam-breaking with water flushing out with all kinds of entanglements."

Horwitz and Day spent much of the day after their story moved being interviewed on television networks and radio, including MSNBC, Fox News, NPR’s Morning Edition. Citing AP’s reporting, Jimmy Kimmel performed an extended riff on ABC’s “Jimmy Kimmel Live!“ about Manafort’s work for the Russian billionaire.

The March 22 story was followed a day later by another Manafort scoop from Washington, this one by Jack Gillum, Menelaos Hadjicostis and Eric Tucker, revealing that U.S. Treasury agents earlier this year obtained information about Manafort's banking transactions from regulators in Cyprus.

For digging up new details about a central figure in the Trump campaign – amid the ongoing federal investigation into Russian interference in the U.S. election – Horwitz and Day win this week’s $500 prize.