As long as Senator Mitch McConnell of Kentucky is running the Senate, major Democratic proposals are going nowhere; his power as majority leader—and a filibuster rule that requires 60 votes for most legislation—makes the chances of success unlikely. As the 2020 primary cranked up to its next level of seriousness with the third debate last night, so did that big question for the Democrats onstage: How exactly are they going to do what they’ve proposed?

Most of the candidates said they were eager for a detailed discussion. Yet none were ready to embrace the challenge entirely. Senator Elizabeth Warren of Massachusetts, for example, tried to avoid directly answering a question about whether middle-class taxes would go up under Medicare for All—even though Senator Bernie Sanders of Vermont, whose plan she’s endorsed, acknowledges they would. (He’s argued that Americans would save money overall on their health-care costs.) And Warren has still never quite explained how she proposes to pass the 2 percent wealth tax that is at the core of her candidacy. Meanwhile, the moderators wanted to know, what is Joe Biden’s plan to counter China’s economic rise if not the Trans-Pacific Partnership, a trade deal he once helped sell but now opposes? How would Sanders get any of his major proposals through the Senate when he still supports keeping the filibuster in place? How would former Representative Beto O’Rourke of Texas build support in Congress for mandatory assault-rifle buybacks? The answers largely remain mysteries.