Sen. John McCain, R-Ariz. (left), and Sen. Lindsey Graham, R-S.C., chat on an escalator on Capitol Hill in Washington in February. The two senators have long been friends and collaborators, but the bond is being tested by the so-called Graham-Cassidy bill, which would dismantle the Affordable Care Act by taking money spent under the law and sending it to states in the form of block grants. File/Al Drago/The New York Times