The Senate Banking Committee voted Thursday to approve, mostly along party lines, legislation that would set the rules for the operation and oversight of digital asset markets, advancing a landmark bill the panel has been working on since last summer.

Months of negotiations between Republicans and Democrats resulted in only two Democrats — Sens. Ruben Gallego of Arizona and Angela Alsobrooks of Maryland — joining all Republicans in a 15-9 vote.

The lack of support from committee Democrats may portend trouble for the measure on the Senate floor, where at least seven Democrats or independents would have to vote in favor, if all Republicans are in support, to overcome a filibuster. The Senate legislation is a…