Forget tax reform. The looming government shutdown could be an even bigger disaster for GOP

• The threat of a government shutdown is descending on the nation's capital in December.
• It would be the first shutdown ever to occur when one party controlled the White House and both chambers of Congress.

Source: HBO

There is no shortage of great entertainment coming from Washington, DC these days. From the ongoing series "How I Met the Russians" to the introduction of "So you think you can reform taxes," the nation's capital is producing "must-see" politics. However, current events are masking tomorrow's looming crisis. Winter is coming to Congress. No, it's not the white walkers from "Game of Thrones," but something much more pernicious: the threat of a government shutdown is descending on the nation's capital in December.

Congress must pass a spending bill or short-term continuing resolution by December 8th. Otherwise the federal government will run out of funds when the stopgap measure agreed to in early September expires. This will require considerable cooperation among Republican rank-and-file which has been in short supply since President Trump disrupted the GOP's long-standing norms. While Republicans may rule the White House and Congress, their patchwork alliance of moderates, traditional conservatives, Tea Partiers, and America first populists is tenuously held together at the moment by an allegiance to tax cuts.

Tax reform is "must-pass" legislation. Failure is not an option. If we don't pass tax reform, we will lose our majorities in Congress. This party unity, or at least the appearance of it for the time being, exists on just one agenda item.

The tax reform veneer is thinly papering over all the major GOP divisions on other issues, like government spending and the debt ceiling. Once tax reform is complete or stalls, these unresolved inter-party battles will reemerge with a vengeance. Come December, Congress will need to fund the government to both avoid a shutdown and spending cuts from sequestration that would be triggered in January absent a deal, threatening both the military's budget and domestic programs.

The current façade of Republican unity will quickly dissipate if GOP leaders ask the rank-and-file to vote for spending increases that are anathema to fiscal conservatism. This is the same GOP that forced a government shutdown in 2013 and ousted its own leader, John Boehner, due to his "insufficient" fiscal conservative bona fides. A December government shutdown would be the first shutdown ever to occur when one party controlled the White House and both chambers of Congress, a stark milestone for government dysfunction. The resulting political disaster for Republicans from such a shutdown would dwarf any failure on tax reform.

Adding to the December difficulty, Republicans cannot just rely on themselves for passing a spending bill even if they are able to achieve unanimity in the Senate. To avoid a filibuster in the upper chamber, Republicans will also need the support of at least eight Democrats. Coming back from exile, an emboldened Democratic Party led by Nancy Pelosi and Chuck Schumer will seek redress on their major policy grievances by threatening to withhold support for a spending bill if certain policy riders are not included.

First and foremost for Democrats is a policy solution for the Deferred Action for Childhood Arrivals (DACA) program. Established by the Obama administration in 2012 for approximately 690,000 young "DREAMers" who are undocumented immigrants, DACA's termination by the Trump administration created a backlash from Democrats.

Beset by protests from their activist base, Pelosi and Schumer are insisting on passing a clean DACA bill without any border security or enforcement measures. Anything measurably different means Democrats are not providing the necessary support to Republicans for keeping the government funded. Republicans, though, have an equally vocal base who would see any such DACA deal as "amnesty" and an act of betrayal. If a DACA provision is included to a spending bill, GOP leaders would face a potential rebellion among House conservatives.

If Democrats are really looking to play hardball in the spending negotiations, they may also insist on reinstating cost-sharing reduction (CSR) payments to subsidize healthcare costs for low-income Americans. Democrats were outraged at the president's action to cut CSR payments, which they considered an intentional sabotage of the Affordable Care Act, and could use the December spending deadline as a point to resume CSR payments.

They will likely demand that Congress vote on a bipartisan deal to reinstate CSR payments through 2019, which was reached by Senators Lamar Alexander (R-TN) and Patty Murray (D-WA). While the deal has the support of 60 senators, including 12 Republicans besides Alexander, GOP opposition in the House to the deal is rampant and will be hard to overcome.

Finally, additional disaster relief spending will be another point of contention in December spending negotiations. Conservatives are making a point to try to offset any more disaster aid with spending cuts. Rep. Mark Walker (R-NC), who leads the 172-member strong conservative Republican Study Committee, penned an op-ed recently, writing, "Congress should pay for these emergency packages by cutting spending in other areas that are less of a priority." But Democrats and several Republicans are likely to reject any spending cuts to complement increased funds for hurricane and wildfire relief.

Strong political leadership can potentially avert a government shutdown. House Speaker Paul Ryan (R-WI) and Senate Majority Leader Mitch McConnell (R-KY) may not be Jon Snow, but they are the only individuals empowered by their fellow Republicans to forge a temporary truce with the Democrats, at least in the absence of any clear heirs apparent. But chaos is a virtue on the iron throne in the Oval Office, and there may not be enough dragon glass in the world to stop winter from coming to Washington, DC.

Commentary by Ben Koltun, a senior research analyst at Beacon Policy Advisors LLC, an independent policy research firm based in Washington, DC.

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