David Fahrenthold reacts to the announcement that he won the Pulitzer Prize for National Reporting at The Washington Post. (Bonnie Jo Mount/Washington Post)

Washington Post reporter David Fahrenthold remembers being struck by Donald Trump’s pledge to donate $6 million, including $1 million of his personal funds, to veterans groups during a televised fundraiser before the Iowa caucuses early last year. Did Trump follow through? he wondered. So, weeks after the event, Fahrenthold started asking questions.

For several months, he found, the answer was no, despite assurances to the contrary from Trump’s campaign. When Trump finally made the donation in late May, the reporter set off on a broader inquiry. In a detailed series of articles, he found that many of Trump’s philanthropic claims over the years had been exaggerated and often were not truly charitable activities at all.

On Monday, Fahrenthold’s investigative digging was rewarded with the Pulitzer Prize, journalism’s most prestigious award. His work documenting the future president’s charitable practices won the award for national reporting.

Fahrenthold’s Pulitzer-winning package of stories also included his article disclosing that Trump had made crude comments and bragged about groping women during an unaired portion of an interview on “Access Hollywood” in 2005.

The story, a result of an anonymous tip, proved to be one of the most consequential and widest-read in the history of campaign reporting; it led to calls for Trump to drop out of the race just weeks before Election Day. The article and accompanying video also prompted two apologies from Trump — who called his comments “locker-room banter” — and inspired some of the themes of worldwide women’s protest marches that drew millions the day after Trump was inaugurated in January.

(McKenna Ewen,Whitney Leaming/The Washington Post)

The Post also had two finalists in this year’s Pulitzer competition, which is administered by Columbia University. Both were recognized for work tied to Trump’s candidacy:

Fred Hiatt, the newspaper’s editorial-page editor, was a finalist in the editorial-writing category for unsigned staff commentaries. Hiatt’s editorials argued against Trump’s candidacy while defending American values and condemning the normalization of bigotry. Hiatt has now been a finalist for the editorial-writing award three times; he was also a finalist for his work in 1999 and 2000.

National reporter Eli Saslow was a finalist in the feature-writing category for stories that explored grievances, despair and racism in pockets of white America, one of Trump’s key constituencies. Saslow won the Pulitzer for explanatory reporting in 2014 and was also a finalist for feature writing in 2013 and 2016.

Fahrenthold’s prize-winning reporting was a follow-the-money tale that combined dogged reporting — he called 450 charitable organizations to ask them whether Trump had ever donated money — with the creative use of social media, especially Twitter, to “crowdsource” the public’s collective knowledge of people and events.

In the process, Post editor Martin Baron said, Fahrenthold, 39, “reimagined” investigative reporting. Traditionally, Baron said, reporters have kept their work “secret and guarded” until they have developed enough information to publish. Fahrenthold instead shared his progress on stories via Twitter and openly asked readers for tips and information that guided his work. Baron noted that this process now has a name: “the Fahrenthold method.”

In one of several memorable examples, Fahrenthold, who joined The Post as an intern in 2000, posted images of the handwritten list of charities he had contacted to ask whether Trump had contributed to them (almost none said he had). He asked readers for names of other likely recipients, receiving dozens of suggestions.

With the assistance of Post researcher Alice Crites, Fahrenthold found that Trump had not donated any of his own money to the Donald J. Trump Foundation since 2008. Instead, he had solicited money from others. He further discovered that the foundation was not registered to make such solicitations, as required by New York state law. The revelation prompted authorities in New York to order the foundation to suspend further fundraising.

He also found several instances in which the future president had spent money from the foundation to buy things for himself and his for-profit companies, potentially violating laws against “self dealing” by a charitable entity.

[eBook: ‘Uncovering Trump: The Truth Behind Donald Trump’s Charitable Giving’]

Trump appeared to do so with some frequency. Fahrenthold revealed that Trump had purchased National Football League player Tim Tebow’s helmet and jersey for $12,000 in 2012 and two massive portraits of himself for $30,000, all with the foundation’s money and without apparent charitable intent.

In addition, Fahrenthold found that Trump had used $258,000 of the foundation’s money to settle lawsuits that involved his private, for-profit businesses. That included a lawsuit by a golfer who claimed Trump had reneged on a $1 million prize in a hole-in-one contest at one of Trump’s golf clubs in 2010. Trump settled with the golfer: The golf club paid nothing. The charity paid $158,000.

The foundation also gave $25,000 in 2013 to a political group supporting Florida Attorney General Pam Bondi (R). The donation came around the time Bondi’s office was considering whether to join a multistate fraud investigation against Trump University on behalf of Florida residents. Bondi eventually decided not to join the effort.

Using Twitter, Fahrenthold asked the public for help in tracking down a four-foot-tall painting of Trump that Trump had purchased with $10,000 of his foundation’s money in 2014. Readers responded by finding a photo of the painting posted on the travel website TripAdvisor.com. The painting had apparently been hung at a Trump-owned club in the Miami area.

An anchor for Univision, Enrique Acevedo, eventually found the painting, fueling another Fahrenthold story. Acevedo reserved a room at the resort and asked workers there whether they had seen the portrait. They directed him to a closed-up bar; Acevedo asked another worker, in Spanish, whether he could look inside. He found the painting hanging on a wall of the bar.

The charity stories elevated Fahrenthold’s profile so high that he became the recipient of an unsolicited tip on the morning of Oct. 7. The still-unnamed caller — only Fahrenthold, Baron and another Post editor know his or her identity — directed Fahrenthold to a bombshell: the unaired video clip of Trump bragging to “Access Hollywood” host Billy Bush that his celebrity status enabled him to “grab [women] by the p---y.”

The publication of the video and Fahrenthold’s story instantly shook up the presidential race.

“The power of it was to hear Trump’s voice,” Fahrenthold said of the clip. “If it had just been a transcript or a summary, it wouldn’t have had the same impact. But to hear it and see it made it horrifying.”

While Trump remained generally silent in the face of Fahrenthold’s continued revelations, the then-president-elect announced just before Christmas that he would shut down his foundation (it technically remains open while the New York attorney general’s office continues its investigation).

The thrust of his reporting, Fahrenthold said, was to examine whether Trump was as honest or as generous as he had long claimed. “I hope I gave people a sense of the moral dimension” of a presidential candidate, he said. “He said he was very generous. [The stories asked], did he really do that?”

Baron, who urged Fahrenthold to stay on the Trump charity beat once the initial controversy about the Iowa fundraiser had died down at midyear, said the reporter “never took things at face value.”

He added: “There’s an old line in journalism that says, ‘If your mother says she loves you, check it out.’ David’s work was in that spirit.”

Among the other journalism winners were:

The International Consortium of Investigative Journalists, a nonprofit based in Washington that led the coverage of the Panama Papers, a huge cache of documents exposing the scale of offshore tax havens. The ICIJ shared the explanatory reporting award with McClatchy and the Miami Herald, which also were part of the Panama Papers reporting.

The New York Daily News and ProPublica, which won the gold medal for public service reporting for uncovering widespread abuse of eviction rules by police to remove hundreds of people, mostly poor minorities, from their homes. The judges singled out reporter Sarah Ryley, formerly of the Daily News, for her work on the joint project.

The New York Times won three Pulitzers, for international reporting, feature reporting and breaking-news photography. The international award was for its staff’s reporting on Vladimir Putin’s authoritarian regime in Russia. The photography award went to freelancer Daniel Berehulak for his photographs of the Philippines’ violent crackdown on drug dealers and users. The feature award was for C.J. Chivers’s story about a Marine’s postwar descent into violence (the finalists in the feature category were Saslow and the Wall Street Journal’s Adam Entous and Devlin Barrett; Entous and Barrett have subsequently joined The Post).