As the Senate wrapped up its work for the year, Sen. Michael Bennet took to the floor of the nearly empty chamber and made a late-night plea for Congress to redouble support for Ukraine: “Understand the stakes at this moment.”

It was the third time in recent months the Colorado Democrat has kept the Senate working late by holding up unrelated legislation in a bid to cajole lawmakers to approve tens of billions of dollars in weaponry and economic aid for Ukraine. During a nearly hour-long, emotional speech, he called on senators to see the nearly 2-year-old conflict as a defining clash of authoritarianism against democracy and implored them to consider what it means “to be fighting on that freezing front line and not know whether we’re going to come through with the ammunition.”

Yet Congress broke for the holidays and is not expected to return for two weeks while continued aid for Ukraine has nearly been exhausted. The Biden administration is planning to send one more aid package before the new year, but says it will be the last unless Congress approves more money.

With support slipping in Congress even as conflicts and unrest rattle global security, the United States is once again struggling to assert its role in the world. Under the influence of Donald Trump, the former president who is now the Republican Party front-runner, GOP lawmakers have increasingly taken a skeptical stance toward U.S. involvement abroad, particularly when it comes to aid to Ukraine.