WHEN WE FIRST wrote in December to applaud the stop-the-dawdling debt reduction effort launched by Sens. Mark R. Warner (D-Va.) and Saxby Chambliss (R-Ga.), the bipartisan group seemed like a potentially useful adjunct to the momentum generated by President Obama’s fiscal responsibility commission in the fall.

Now, with the president having failed to offer leadership and House Republicans frittering away their energies on a tiny slice of the budget, the Warner-Chambliss effort is looking like the only game in town. It has evolved into the newest Gang of Six, the two senators plus their Republican and Democratic colleagues who served on the commission and voted for its recommendations: Republicans Tom Coburn of Oklahoma and Mike Crapo of Idaho and Democrats Richard J. Durbin of Illinois and Kent Conrad of North Dakota. They should be doubly commended: first for doing the difficult work of translating lofty commission talk into concrete legislative action; second, for being willing, in a time of ideological rigidity, to accept that painful trade-offs will be essential to putting the country on a sustainable fiscal path.

This won’t be easy, politically or substantively. Already, the Democrats have come under fire from Senate leaders for considering changes to Social Security benefits. Anti-tax purist Grover Norquist warned the Republican senators about being “implicated as parties to a bipartisan budget deal containing a net tax increase,” in apparent violation of their no-new-taxes pledge. Exactly how to balance spending cuts with revenue increases will entail wrenching debate about the size and role of government. The question of how targets for specific cuts would be enforced is especially complex: Would programs for the poor be imperiled if enough is not cut or raised elsewhere? There’s a risk that the painful choices needed to produce a package acceptable to a supermajority of senators would be treated as the opening bid for House Republicans to ratchet even further in the direction of cuts.

Nonetheless, at a time when everyone is happy to talk about the need for adult conversation, the Gang of Six is actually having one. They’re debating numbers, deadlines, legislative methods. That’s an important start. Maybe at some point Mr. Obama will decide to join in.