WASHINGTON — First, it was about adoption. Then, it was a routine effort to get political dirt on rival Hillary Clinton. Now, President Donald Trump says that, "to the best of my knowledge," there was no follow-through on a meeting between his namesake son, his son-in-law, his indicted former campaign manager and Russian emissaries who claimed to have incriminating information on Clinton.

“Don has received notoriety for a brief meeting, that many politicians would have taken, but most importantly, and to the best of my knowledge, nothing happened after the meeting concluded,” the president said in a statement to The Washington Post.

The sitdown at Trump Tower has become a focal point for investigators looking into Russia's interference in the 2016 presidential election, whether Trump or his campaign conspired with Russia and whether Trump or other administration officials obstructed justice after he won the election.

Trump's insistence that "nothing happened" afterward — true or not — likely wouldn't affect any possible conspiracy charges, former federal prosecutor Glenn Kirschner said in a telephone interview with NBC News.

"No, it doesn’t matter," Kirschner said, noting that a person can be charged with conspiracy to commit murder even if no one is killed.

On a public relations level, at the very least, Trump and Trump Jr. have been bedeviled by their own shifting narrative on the purpose of the June 9, 2016, meeting and what happened inside the landmark New York tower that bears their name.

When The New York Times first reported on the Trump Tower meeting in July 2017, Donald Trump Jr. replied with a statement citing adoption as the major subject of discussion.

"It was a short introductory meeting," he said in a statement. "I asked [Trump son-in-law] Jared [Kushner] and [campaign manager] Paul [Manafort] to stop by. We primarily discussed a program about the adoption of Russian children that was active and popular with American families years ago and was since ended by the Russian government, but it was not a campaign issue at the time and there was no follow up. I was asked to attend the meeting by an acquaintance, but was not told the name of the person I would be meeting with beforehand."

The president, aboard Air Force One, dictated the statement issued by his son, as The Washington Post reported. For months, his aides insisted he did no such thing. But his lawyers finally acknowledged earlier this year that the elder Trump did personally dictate his son's misleading statement.

Trump Jr. changed his story quickly — one day later — after being faced with reporting that opposition research on Clinton was the bait for the meeting.

"After pleasantries were exchanged, the woman stated that she had information that individuals connected to Russia were funding the Democratic National Committee and supporting Ms. Clinton," Trump Jr. said. "Her statements were vague, ambiguous and made no sense. No details or supporting information was provided or even offered. It quickly became clear that she had no meaningful information. She then changed subjects and began discussing the adoption of Russian children and mentioned the Magnitsky Act. It became clear to me that this was the true agenda all along and that the claims of potentially helpful information were a pretext for the meeting.”

When told that he might receive documents that would hurt Clinton, as part of "Russia and its government's support" of his father, Trump Jr. emailed back to an intermediary: "If it's what you say I love it especially later in the summer."

The president has consistently defended his son, but distanced himself from the meeting.

"Most politicians would have gone to a meeting like the one Don jr attended in order to get info on an opponent," Trump wrote on Twitter last year. "That's politics!"

Last week, as the meeting came back into focus in the news, the president added that "I didn't know about it!"

Fake News reporting, a complete fabrication, that I am concerned about the meeting my wonderful son, Donald, had in Trump Tower. This was a meeting to get information on an opponent, totally legal and done all the time in politics - and it went nowhere. I did not know about it! — Donald J. Trump (@realDonaldTrump) August 5, 2018

It remains to be seen whether the storyline will evolve again. For now, the president is trying to send the message that he wasn’t aware of what his son was doing — even if, as he says, none of it was wrong.