Back in March, the Hill newspaper published a series of stories and interviews that seemed, at the time, to be mainly of interest to foreign-policy wonks.

John Solomon, the paper’s executive vice president, interviewed Ukraine’s then-top prosecutor, Yuri Lutsenko, who alleged a startling conspiracy: that law enforcement officials within his country had leaked damaging information in 2016 against Paul Manafort, President Trump’s former campaign chairman, to help Democrat Hillary Clinton’s presidential campaign.

Lutsenko also floated suggestions that Marie Yovanovitch, who was then the U.S. ambassador to Ukraine, was cooperating with the scheme to help Clinton and undermine Trump’s campaign. The ambassador, Lutsenko alleged, was “interfering in his ability to prosecute corruption cases” and had even given him a list of defendants that he would not be allowed to prosecute, Solomon wrote.

Solomon’s piece urged “a serious, thorough investigation” of Lutsenko’s claims.

The story touched off a brushfire within the conservative media, in which Solomon is a prominent figure, but stayed largely out of mainstream view.

On Thursday, however, Solomon’s work gained new attention — and raised new questions about its sourcing, credibility and motivation. In a complaint filed by an anonymous whistleblower, Solomon’s stories were cited as part of a narrative about the alleged effort by Trump and his allies to pressure Ukraine’s government into digging up dirt on Trump’s Democratic rivals, including Clinton and Joe Biden, to enhance his prospects for reelection next year.

What’s clear is that Solomon — a former Washington Post investigative reporter who later became editor of the conservative Washington Times — has played an important role in advancing a flawed, Trump-friendly tale of corruption in Ukraine, particularly involving Biden and his son Hunter. The younger Biden was a director of a Ukrainian energy company at the time his father, the vice president, was beseeching Ukrainian officials to crack down on corruption.

Solomon’s stories, in turn, have been echoed and amplified by Trump, his son Donald Jr. and Trump’s personal lawyer, Rudolph W. Giuliani, who has been at the heart of Trump’s effort to extract damaging information from Ukrainian officials about the Bidens.

Trump and his son, for example, highlighted Solomon’s Lutsenko story to accuse Yovanovitch, an appointee of President Barack Obama, of disloyalty and political betrayal.

After Solomon appeared on Sean Hannity’s Fox News program in March to promote Lutsenko’s allegations, President Trump tweeted a reference to Solomon’s Hill story. A few days later, Trump Jr. tweeted a link to a story published by the conservative Daily Wire that reprised Solomon’s claims about Yovanovitch.

A week later, Solomon was back on the Ukraine story, this time raising “some hard questions,” as he put it, about the Bidens’ diplomatic and business activities in the eastern European nation. In an interview on Fox News a few days later, Giuliani urged the Justice Department to look into the matter.

Trump seemed to put the biggest bow of all on Solomon’s work, telling Hannity in an interview in late April that Lutsenko’s claims were “big” and that Attorney General William P. Barr “would want to see this.”

Except both stories had major defects. The State Department called Lutsenko’s allegations against Yovanovitch “an outright fabrication.” And Lutsenko eventually backed off, retracting his claim in April that the ambassador had given him a do-not-prosecute list. He further said in May that there was no evidence of wrongdoing by Joe Biden or his son. (Lutsenko was eventually replaced as chief prosecutor by Ukraine’s reform-minded new president, Volodymyr Zelensky.)

Nevertheless, in May, Trump recalled Yovanovitch from her ambassadorial post early — a move top Democratic lawmakers called “a political hit job.” In the report released Thursday, the whistleblower says this was a result of Lutsenko’s unfounded allegations.

Solomon did not respond to requests for comment about his reporting of the Ukraine story. But in a tweet Thursday afternoon, he wrote: “I stand by my stories 100 percent, all of which are completely accurate and transparent. We embedded the documents and videos we collected in each story for all to see.”

Hill editor in chief Bob Cusack referred a request for comment from the paper to another executive, who did not respond.

Solomon, 52, has had a long, and occasionally decorated, career as an editor and investigative reporter in Washington, though his more recent work has been trailed by claims that it is biased and lacks rigor.

His career includes nearly 20 years at the Associated Press and shorter stints at The Post, Washington Times, the Center for Public Integrity, Newsweek/the Daily Beast and Circa, an online news outlet that was closed by its owner, Sinclair Broadcast Group, in March. He also co-founded an online publication titled the Washington Guardian.

At The Post, he was a hard-charging national investigative correspondent, with a knack for turning out important stories — such as one in 2007 detailing Giuliani’s efforts to enrich himself after serving as New York’s mayor on Sept. 11, 2001.

Over the past decade or so, his work has taken on a more conservative cast. His prominence within the conservative media ecosystem has been abetted by Fox News’s Hannity, who has featured him in segments highlighting his columns, particularly those casting doubt about special counsel Robert S. Mueller III’s investigation of Trump’s ties to Russia.

The attention from Hannity — a fierce supporter of the president — has led other conservative outlets to aggregate Solomon’s work, boosting his influence.

But Solomon has left a trail of critics, too.

The Columbia Journalism Review, in one of several critiques of Solomon, wrote in 2012 that he “has a history of bending the truth to his story line” and “distorting facts and hyping petty stories.”

He has been a figure of some controversy within his own shop, the Hill, which he joined in 2017 as an “investigative columnist” and the head of its video unit. In late 2018, a group of newsroom staffers complained that his stories about a liberal lawyer’s effort to raise money for women who had considered making sexual misconduct allegations against Trump during the 2016 campaign lacked adequate context.

He also reported, in an October 2017 column, that Russian sources had paid Bill Clinton $500,000 for a speech and waged “an influence campaign” with then-Secretary of State Hillary Clinton at the time the Obama administration approved the sale of an energy company, Uranium One, to a Russian company, suggesting but not confirming a quid pro quo.

Similar internal complaints at the Hill trailed another Solomon-authored story that was favorable to Trump. Other news organizations have reached unfavorable verdicts on his columns.

Solomon said last week that he was moving on again, announcing that he was leaving the Hill next week to start his own, unspecified online media venture.