Over the last five decades, there have been 21 federal shutdowns: 2019: Under Trump. Lasted 35 days and cost the economy about $3 billion, equal to 0.02% of GDP, according to the Congressional Budget Office. USA TODAY's Michael Collins and Olivia Munson, Reuters contributed to the reporting of this story.

When would a federal shutdown start? Which parts of the government would shut down? Will payments to Social Security recipients be affected?

With a funding deadline approaching, workers are bracing for the possibility of a disruptive holiday season, which could include longer wait times for travelers.