A group of Democrat senators — including Elizabeth Warren of Massachusetts, Kamala Harris of California and Kirsten Gillibrand of New York, all aspiring presidential nominees — collaborated on a measure to prevent Mr. Trump from using funds appropriated for disaster relief to pay for border wall construction.
Mr. Trump made the wall his signature promise on the 2016 presidential campaign trail, where he was cheered by supporters chanting, “Build the wall,” only to be frustrated that he was unable to do so during his first two years in office, when Republicans controlled both houses of Congress.
In waging a shutdown battle over the barrier, he has made it the nearly singular focus of his presidency in his third year in office. But Democrats, who took control of the House in January, have made blocking it just as high of a priority, leaving the two sides at a stalemate.
Negotiations since late December ultimately went nowhere. Speaker Nancy Pelosi, who led Democrats to power in the House, went beyond simply criticizing the wall as unwise or ineffective by declaring it “immoral,” drawing a hard line even though many Democrats have voted for fencing along parts of the border in the past.
At one point during the shutdown, Mr. Trump asked Ms. Pelosi if she would be willing to support the wall in 30 days if he agreed to reopen the government. When she said no, he got up and walked out of the room with a sharp “bye-bye,” then posted a message on Twitter declaring talks a “waste of time.”
Mr. Trump’s national emergency declaration could provoke a constitutional clash between the president and Congress. Under Article I of the Constitution, Congress has the power to appropriate funds. “No money shall be drawn from the Treasury, but in consequence of appropriations made by law,” it says.
But Congress has passed laws in the past providing presidents with authority in national emergencies, laws that remain on the books. Scholars pointed to two that could be used by the Trump administration to justify a presidential expenditure for his border wall without explicit legislative approval.