WASHINGTON — President Trump ran for office on a promise to end politics as ­usual.

But Monday morning, Trump posted a defense on Twitter of his son’s meeting with a Russian lawyer, who had promised sensitive government information that could be damaging to Hillary Clinton, by saying that it was simply politics as usual.

Trump’s newest tweet about his elder son, Donald Jr., and a controversial meeting June 9, 2016, at Trump Tower, described the gathering as routine and something almost anyone in his current line of work would do.

“Most politicians would have gone to a meeting like the one Don Jr. attended in order to get info on an opponent,’’ Trump posted on his Twitter account just after 10 a.m. “That’s politics!’’

But interviews with politicians by various news outlets have revealed that few elected officials were willing to say they, too, would have taken such a meeting, given how it was described in an e-mail to the younger Trump.

The president’s defensive stance about his son was in keeping with what he has said for a week about the meeting.

The younger Trump met with the lawyer, Natalia Veselnitskaya, in the Trump Tower offices after an acquaintance said she had damaging information about Clinton.

He initially told The New York Times that it was about Russian adoptions. A day later, he acknowledged that it had initially been about supposedly harmful information on Clinton, Trump’s rival in the general election.

In addition, the meeting was described initially as having five attendees, including Trump’s brother-in-law, Jared Kushner, and the campaign chairman at the time, Paul Manafort. In the days since the meeting was first reported, that number has grown to seven attendees.

The president has insisted he learned of the meeting only a few days before The Times article. His aides helped write his son’s initial statement describing the meeting as they flew back with the president from the Group of 20 summit meeting in Europe.

The White House has found itself unable to take control of the narrative, with new revelations coming almost daily

Also Monday, three Senate Democrats called on the White House to review and possibly revoke Kushner’s security clearance because of his attendance at the meeting with the Kremlin lawyer.

Kushner, a senior adviser to Trump, disclosed the meeting on his security clearance paperwork, but Democrats questioned how much he disclosed.

Democratic Senators Richard Blumenthal of Connecticut, Al Franken of Minnesota, and Mazie Hirono of Hawaii said in a letter to the White House that given the meeting, Kushner’s top access ‘‘may pose a danger to this country.’’

►A federal official says the US has an ethics crisis. A7