Mitch McConnell: Boy, this is a tough problem. Photo: Bill Clark/CQ-Roll Call,Inc.

Senate Republicans have unveiled their version of a plan to cut taxes, and it differs from the House version in some relatively small ways. But the primary issue is one that most news coverage has addressed only in passing: The Senate bill, like the House bill, cannot pass under current Senate rules.

Republicans set out not to repeat the experience of having a tax code with an automatic expiration date. That’s why they have worked so hard to come up with revenue sources like a border-adjustment tax, which could replace the lost revenue from their tax cuts. But those ideas all collapsed politically. And they don’t have any better ideas.

It’s possible they’re hoping to find eight Democratic senators to support this bill, which would allow them to pass it through regular rules rather than budget reconciliation. (It seems wildly unlikely that Dems would go for it.) It’s also possible they’re planning to blow up the Senate’s budget-reconciliation rules (more likely, but would still take 50 votes, and some Republicans are pretty leery about changing the rules to weaken the filibuster). Or they just have no idea what to do and are punting the problem they had months and months to solve until later.