Dan Janison Melville. N.Y. Tuesday January 26, 2010. Daniel Janison,

Dan Janison has been a columnist at Newsday since 2007.

Changing your story can undercut your credibility.

This is true whether you’re Donald Trump Jr. or a witness the cops brought in for questioning.

It is true even if you don’t recant the earlier version, but only add key details you omitted.

Back in March, the namesake son of the new president was quoted as saying: “Did I meet with people that were Russian? I’m sure, I’m sure I did. But none that were set up. None that I can think of at the moment. And certainly none that I was representing the campaign in any way.”

Now, however, the junior Trump confirms arranging and attending a Trump Tower meeting in June 2016 with a Kremlin-connected lawyer. It included his brother-in-law Jared Kushner and his father’s then-campaign manager Paul Manafort.

On Saturday the first son issued a statement — once word of the meeting’s disclosure to government officials had leaked out.

The June 9 meeting was short, he said. They talked about an adoption program for Russian children, he said, “which was not a campaign issue at the time and there was no follow up.”

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That made it all sound pretty innocuous.

But by Sunday, The New York Times had prodded Trump Jr. and his handlers to give a different, more forthcoming account.

Like the first statement, it was clearly crafted in a lawyerly way. This makes sense, given the likelihood Trump Jr. will need to swear to it at some point in the federal Russia probe. It is rare for a public-relations line to change so quickly.

As Trump Jr. now tells it, he was “asked to have a meeting” — by an acquaintance involved in the Trumps’ Miss Universe pageant four years earlier — “with an individual who I was told might have information helpful to the campaign.”

Russian lawyer Natalia Veselnitskaya said she had “information that individuals connected to Russia were funding the Democratic National Committee and supporting Mrs. Clinton,” Trump Jr. says.

That sounds a lot less innocuous than the first statement.

The account of Veselnitskaya’s pitch is jarring when you consider U.S. intelligence agencies report Russian hackers carried out cyberattacks targeting Clinton and the DNC.

The younger Trump’s latest narrative makes him seem judicious. The Russian attorney’s statements were “vague, ambiguous and made no sense,” he says. “No details or supporting information was provided or even offered.”

Rob Goldstone, the acquaintance who asked for the meeting, said in his own statement that once the lawyer broached the Russian adoption policy, “the meeting was halted by Don Jr. and we left.”

Tactically, the statements leave room for the Trump team to keep denying the widespread but hazily defined suspicion of “collusion” with Russian officials.

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Indeed, Trump Jr. followed in the family tradition of jeering in the Twittersphere.

On Monday, he tweeted sarcastically: “Obviously I’m the first person on a campaign to ever take a meeting to hear info about an opponent . . . went nowhere but had to listen.”

Obviously that won’t be the final word in a public drama and an investigation that have a long way to go — with other facts still to be pulled out of those in the spotlight.