Senate Republican leaders continue to scrounge for votes to pass Donald Trump’s $3.3 trillion tax and spending bill as lingering intraparty fights threaten to upend the legislative centerpiece of the president’s domestic agenda.

Senate Democratic Leader Chuck Schumer of New York said the “hardest choices” for Republicans are still to come. His side plans to bring “amendment after amendment after amendment to the floor, so Republicans can defend their billionaire tax cuts and so they can try to explain their massive cuts to Medicaid to people back home.”

Senate Republicans hope they are hours away from passing their massive tax and immigration bill. But the outcome is far from certain.