Senate Republicans narrowly pushed through a procedural vote to open debate on plans to repeal and maybe replace the Affordable Care Act Tuesday—but then suffered a defeat only hours later when Republicans failed to muster enough votes to pass their replacement bill.

First, on Tuesday, the Senate voted 50 to 50 to open the debate, with Vice President Mike Pence then breaking the tie. Two Republican senators, both women—Susan Collins of Maine and Lisa Murkowski of Alaska—joined Democrats in voting against the motion to proceed. Arizona Senator John McCain returned to Capitol Hill to cast a decisive vote to open debate, only a week after being diagnosed with brain cancer.

But once the debate began, divisions within the Republican Party over a replacement bill doomed their efforts to push through any legislation. Nine Republicans joined Democrats in rejecting the first healthcare proposal, which would cause more than 20 million people to lose their health insurance. The Republicans needed 60 votes to pass the bill but ultimately received only 43. Throughout the day, Republican lawmakers faced massive protests in the Senate chamber, at offices across Capitol Hill and even on the doorsteps of their own homes, with nearly 100 people arrested.