WASHINGTON — Much of the federal government officially shut down early Saturday morning after Senate Democrats, showing remarkable solidarity in the face of a clear political danger, blocked consideration of a stopgap spending measure to keep the government operating. The shutdown, coming one year to the day after President Trump took office, set off a new round of partisan recriminations and posed risks for both parties. It came after a fruitless last-minute negotiating session at the White House between Mr. Trump and Senator Chuck Schumer of New York, the Democratic leader. With just 50 senators voting in favor, Senate Republican leaders fell well short of the 60 votes necessary to proceed on the spending measure, which had passed the House on Thursday.
Five conservative state Democrats voted for the spending measure. Five Republicans voted against it, although one of those, Senator Mitch McConnell of Kentucky, the majority leader, did so for procedural reasons. As the clock ticked toward midnight, when funding for the government was set to expire, senators huddled on the floor of the crowded Senate chamber, searching for some way forward. Then, in the early morning hours, Mr. McConnell proposed a measure that would keep the government open for another three weeks, not four as the House measure would have done, and said the Senate would come back to into session at noon Saturday.