House Democrats were making plans to undermine US President Donald Trump at his January 29 "State of the Union" address.
The leadership's communications arm sent an email to lawmakers urging them to bring federal workers or other "message-related" guests to the nationally televised event.
House Speaker Nancy Pelosi decided on a more confrontational approach.
Addressing a closed-door meeting of House Democrats, the Speaker read a letter she had just sent to Trump asking him to either postpone the speech until the federal government reopens or deliver the text in writing, citing security concerns.
Surprised Democratic lawmakers cheered their leader's rationale: If the government stays shut down, Pelosi would deprive Trump of the spotlight he craves.
To a President especially sensitive to acts of disrespect — and one with a hearty appetite for pomp and circumstance — the so-called unvitation was not merely a power play. It was a calculated personal slight.
In the two weeks since she reclaimed the speaker's gavel, Pelosi has moved aggressively to leverage her decades of congressional experience to needle, belittle and undercut Trump with swipes at his competence and even his masculinity.
The two leaders are locked in a standoff over a partial government shutdown instigated by Trump's demand that US taxpayers fund a portion of his promised border wall. Both Trump and Pelosi are gambling that the other will bear the brunt of the blame as the economic impact worsens.
In her letter to Trump, Pelosi said the US Secret Service and the Department of Homeland Security have been "hamstrung" and therefore should not bear the burden of securing the President's address in the House chamber.
The White House had no immediate response, but Homeland Security Secretary Kirstjen Nielsen said her department and the Secret Service were "fully prepared to support and secure the State of the Union".
Marc Short, the Trump White House's former legislative affairs director, said if security truly were Pelosi's concern, she would not have extended a formal invitation to Trump to deliver the address, which she did this month after the shutdown began.
Pelosi's strategy for dealing with Trump was born of exasperation, advisers said. She has been deliberately trying to get under his skin and "to talk to him in a way he understands," according to one person familiar with her views.
After Pelosi and Senate Minority Leader Charles Schumer's December 11 Oval Office meeting with Trump, she told House Democrats their session was like "a tinkle contest with a skunk" and that she felt his wall demand was "like a manhood thing for him," according to an aide in the room.
She has implied he cannot relate to the workers affected and "thinks maybe they could just ask their father for more money," a reference to the President's inherited wealth.
And she has described his behaviour as unstable and childish.
"It's a temper tantrum," Pelosi said after Trump stalked out of a negotiating session last week. "I'm the mother of five, grandmother of nine. I know a temper tantrum when I see one."