Senate Majority Leader John Thune can afford to lose three Republican senators and still pass the bill, and there are more than that, right now, who have problems with it. Like the House, he will have to balance the concerns from moderate and conservative members of his conference.

House Republicans were jubilant after muscling through President Trump’s tax and immigration package by a single vote. But across the Capitol, senators were more cautious.

The Senate is poised to take up the Republican megabill after it narrowly passed in the House. But ongoing disputes and a slim majority mean more obstacles ahead.