Want to know why Democrats are failing to optimize their role as the true economic populists against the purely symbolic faux-populism of Donald Trump? Consider the bill to weaken the Dodd-Frank Act, now working its way through the Senate.

The bill would exempt financial institutions as large as $250 billion in assets from many of the safety and soundness regulations of Dodd-Frank. In a world of multitrillion-dollar banks like Goldman, that sounds like a medium-sized operation, but it includes giants such as American Express.

Pure Republican mischief, right? If only. The bill’s lead sponsor is Senator Mike Crapo of Idaho, who chairs the Banking Committee. But the bill has 11 Democrats as co-sponsors.

They include Dems from swing states up for re-election such as Heidi Heitkamp of North Dakota and Joe Donnelly of Indiana—but also Wall Street Dems with safe seats such as Mark Warner of Virginia. Moreover, the idea that Democrats in purple states should posture as “moderates” is hogwash. Maybe they need to be moderate on some social issues, but they would do much better channeling the grievance of regular people and running as populists.

If ever there was a moment not to blur differences between Republicans and Democrats, this is it. Truth to tell, this is not about campaign tactics. It’s about campaign finance.