WASHINGTON—Much of the federal government officially shut down early Saturday 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. But senators from both parties were scrambling for a new deal to reopen the government quickly, possibly just hours after the midnight deadline passed. With just 50 senators voting in favour, 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, Sen. 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 chamber, searching for some way forward. But lawmakers simply ran out of time. The government shutdown was one year to the day after U.S. President Donald Trump took office.