The legislation, which sets rules of the road for stablecoins, is the product of months of negotiations and had been expected to sail through the Senate.

Senate Democratic defections from a bipartisan stablecoins bill could become a procedural hurdle as Republicans try to bring the measure to the floor, possibly as early as this week. Four Democrats on the Senate Banking Committee who voted on March 13 to approve legislation that would facilitate issuance of stablecoins — digital currencies pegged to