Senate Majority Leader Mitch McConnell (R-Ky.) talks with reporters in the U.S. Capitol on Nov. 28. Republicans in the Senate hope to pass their tax cut legislation this week. (Photo by Chip Somodevilla/Getty Images)

The Senate has begun debate on the Republican tax plan. GOP leaders have yet to nail down either final details of the bill or 50 GOP votes to pass it. As GOP leaders continue to negotiate and senators consider possible amendments, most of Washington’s attention is on policy. But process matters too.

Here are three observations about the ways in which process matters for the GOP tax plan.

1. The GOP still isn’t using “regular order,” whatever that means

The demise of “regular order” contributed to the GOP’s failure earlier this year to repeal and replace the Affordable Care Act. Sen. John McCain (R-Ariz.) most pointedly argued that the legislative process stunk:

We seem convinced that majorities exist to impose their will with few concessions and that minorities exist to prevent the party in power from doing anything important. That’s not how we were meant to govern.

Similar concerns could still lead McCain (and perhaps his Arizona colleague, Jeff Flake) to oppose their party’s tax bill, in part because neither faces reelection, although for different reasons.

“Regular order” is hard to define. For some, “regular order” simply means a return to past modes of legislating, in a manner that’s more bipartisan and less structured — or what political scientist Steven Smith once termed “collegial” patterns of lawmaking on the Senate floor. Others say that regular order means allowing committees rather than party leaders to craft policy. Still others use “regular order” as a call to colleagues to stop filibustering every vote. Whatever it means precisely, it evokes a more fluid, collegial process that is no longer used in today’s more partisan Senate and polarized Washington.

Certainly, GOP leaders’ handling of the tax bill entirely avoids any conception of regular order. Under the GOP’s self-imposed deadline of sending a bill to the president by year’s end, the Senate Finance Committee marked up the bill after hearing just an initial assessment of the bill from the Joint Committee on Taxation (JCT), Congress’s official scorekeeper for changes to the tax code. The Senate has started debate on the bill without waiting for the JCT’s final score of the bill’s impact on economic growth.

Without subjecting the bill’s provisions to expert analysis, the bill’s likely effects — let alone its unintended consequences — are unknown. One outside tax analyst remarked, “There are more ticking time bombs in this bill than a Road Runner cartoon.”

Senate leaders also continue to negotiate the bill’s details in secret, just as they did this summer in crafting the health-care repeal bill. And as with this past summer’s effort, even senators who are trying to negotiate changes in the pending bill are being kept in the dark. The tax bill may yet pass, but not because leaders improved the process.

2. Avoiding the filibuster has a steep cost

GOP leaders have used the same special budget vehicle known as “reconciliation” for pursuing both health-care and tax agendas. In exchange for allowing reconciliation bills to pass by a simple majority vote, budget law narrowly limits the scope and cost of the bill.

Using reconciliation for tax cuts directly shapes what the GOP can do to policy. That’s most visible in Republican leaders’ decision to make corporate tax cuts permanent, while allowing individual income tax cuts to expire after a decade. Republicans made that choice to comply with a reconciliation rule that prohibits increases in the federal deficit beyond the bill’s 10-year “budget window.”

Process matters because it determines the bill’s winners and losers. Constrained by budget rules, according to nonpartisan tax analysts, GOP leaders opted to protect corporations and the wealthy. In contrast, although most middle-class households would see at least a small tax cut for 2018, a decade later taxes would likely go up for many of those same households. These policy choices no doubt drive the bill’s remarkable unpopularity.

3. Process amplifies partisanship and makes policy worse

Since World War II, Congress’s landmark laws have typically been passed with bipartisan support. We still see an occasional bipartisan deal, but in our era of ideologically polarized and electorally competitive parties, Congress more often deadlocks.

Relying on reconciliation, however, is costly, in three ways, as I’ll explain below. It amplifies the partisanship that drives its use in the first place. It arguably makes policy worse. And reconciliation spotlights cleavages within the majority party, making it harder to blame the opposition for legislative failure, as we saw with the health-care vote.

Those costs are a big deal. Eliminating the need for Democratic votes reduces already-low incentives for bipartisan cooperation. Even red-state Senate Democrats — who have strong electoral incentives to consider the GOP’s tax plan — note that they have been shut out of the process. The result isn’t just a more partisan Congress. Had Republicans sought the votes of more moderate Democrats, they wouldn’t have been constrained by the dictates of reconciliation: They could have pursued real tax reform, not just cuts, with 60 votes and therefore the ability to defeat any filibuster.

Instead, Republicans — desperate to show voters they can govern and fearing the loss of an Alabama Senate seat that could cut their majority to 51  — speed ahead on a tax bill that experts say would expand government debt, not growth.