Not since the U.S. Supreme Court decision in Bush v. Gore—Tuesday marks the 17th anniversary of its announcement—have we had a December as politically momentous as the one shaping up this year. Which is no small thing because it includes the Decembers leading into the 2004, 2008, 2012, and 2016 presidential-primary and caucus seasons.

Alabama’s special Senate election on Tuesday will determine whether the Republican Senate majority will be two or three seats—the former considerably more precarious than the latter in the fight for Senate control. The results in the Yellowhammer State will be interpreted either as a Scott Brown-like signal or a reminder to Democrats of how challenging the Senate map is this election cycle, as they defend seats in some very conservative and Republican states. Readers will remember that Brown’s January 2010 special-election victory in Massachusetts turned out to be a foreshadowing of a national general election in November that was horrific for Democrats, with the loss of 63 seats in the House and control of that chamber, and six seats in the Senate. It was a huge psychological victory for Republicans, and it gave them even more momentum than they had before.

Add to the mix Sen. Al Franken’s decision last week to resign, setting up a November 2018 special election for that seat, and former Democratic Gov. Phil Bredesen’s decision to run for Bob Corker’s open Senate seat in Tennessee. That means there are two more competitive Senate races than had been expected. While Minnesota is widely viewed as a Democratic state, it has been gradually becoming less so. Recall Franken’s narrow 312-vote win in 2008, as well as the recent presidential-race trend line. Barack Obama won Minnesota by 10.2 points in 2008 and then by 7.7 points in 2012, and Hillary Clinton eked it out by 1.5 points in 2016. Many of the dynamics that contributed to Donald Trump’s win next door in Wisconsin were evident in Minnesota, only a little less so.

In Tennessee, where the Republican hold on the state is awfully strong, the question is whether Bredesen can ride the favorable environment for his party nationally to victory in a tough state, in the manner of Heidi Heitkamp in North Dakota, Jon Tester in Montana, and Joe Manchin in West Virginia. Certain candidates can crack the code and win in places where they shouldn’t. But sometimes the political undertow, either in a specific state or nationally, can be so great that even Olympic-level swimmers can be pulled under, whatever their putative political advantages.

In short, the developments in Minnesota and Tennessee just add greater volatility to a fight for the Senate that was already highly uncertain. The Cook Political Report has now shifted both states into the “Toss Up” column until more data is available, with each party having one more headache than it had a few months ago. Rather than seeing each as a 50-50 proposition, as a Toss Up rating implies, consider each as amorphous, with too many unknowns to favor either side at this early stage.

The final December uncertainty is the tax bill—what form it takes coming out of a House-Senate conference, how voters perceive it, whether success in pushing this top Republican priority outweighs the grave reservations and intense opposition that it has engendered among independents and Democrats. We won’t know the final answers to these questions for almost 11 months.

The fight next year essentially comes down to the question of which will be more important—the prevailing political winds, assuming they continue in the direction and with the velocity we see today; or the political geography, encompassing which seats are up where, the political terrain in each specific state or district, the types of voters in each place, and voting behavior in each one.

Republicans could hardly face tougher headwinds, nor could Democrats face a tougher map in terms of which states have Senate seats up next year and where the congressional district boundaries were drawn for this decade back in 2011. Given that 36 governorships and 6,066 state legislative seats (82 percent of the total) are up next year, the outcome of those state races may well have decade-long redistricting implications, as the 2010 election did. Back then, Republicans were able to capitalize on President Obama’s low standing in the polls and the midterm bias against the party whose president is in the White House.

Republicans now have to worry about those dynamics working against them. Most of these state races are on a four-year cycle, leaving the Republicans disproportionately exposed to losses because of their banner years in 2010 and 2014, the last time these offices were in play. Because of those past drubbings, Democrats have relatively little to lose.

This story was originally published on on December 12, 2017

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