A looming legal battle over President Joe Biden’s vaccine mandate for larger companies will test the limits of his authority to implement sweeping COVID-19 rules, creating potential complications for a Democratic Party that has recently begun to reevaluate the politics surrounding its pandemic policies in light of last week’s electoral defeats.

The 5th Circuit Court of Appeals handed the mandate’s opponents a temporary victory on Saturday when a panel of its federal judges paused the forthcoming vaccine requirements in response to a lawsuit from a business owner and workers in Southern states.