Montana Election Bolsters Predictions of a Large “Democratic Wave”

Democrats performed better than expected in Montana’s special election Thursday, suggesting a large “Democratic wave” is coming.

G. Elliott Morris

May. 26, 2017

Categories: 2018 Midterms Tags: mtal elections special

On Wednesday, May 24th, the Republican candidate for Montana’s at-large congressional district essentially beat (body slammed) a reporter. Then, on Thursday, Greg Gianforte also beat his Democratic opponent Rob Quist in the race for the district’s House seat. Gianforte’s victory cut against some pundits’ expectations of a Democratic pickup — granted, he did break a reporter’s glasses while otherwise being a flawed candidate — and squashed hopes of Democrats being able to flip deep red House seats. But, Democrats may not need seats like Gianforte’s to make big gains in 2018. The next body to be slammed may be the Republican’s House caucus.

In recent special elections to the US House, Democrats have been exceeding expectations left and right. This has prompted belief in a “Democratic wave” (a shift from Republican elected officials to Democratic), and rightly so. On average, Republican House candidates have been underperforming their benchmarks — a statistic often used over at FiveThirtyEight that uses a weighted average of a district’s relative margin in the past two presidential elections — by 15.3 percentage points or so. All of this held true in Montana where Democratic candidate Rob Quist exceeded expectations by a very predictable 15.2 percent.

Democrats are Making Waves in House Special Elections
Margin (%)
(Positive = Dem Win)
Election Trump/Romney
Shift (%)
*indicates primary election, no general election yet
^indicates polling average, not used in average

Source: DailyKOS, FiveThirtyEight
KS 04 -29.2 -6.8 22.4
MT AL -21.3 -6.1 15.2
CA 34 69.5 86.1* 16.6
GA 06 -9.35 -2.2* (1.6^) 7.2* (11^)
SC 05 -19.15 (-17^)
AL Sen -26.7
Average 15.3%

The Montana election is thus yet another data point that suggests Republicans are going to have a hard fight come 2018. Statistically speaking, that data point doesn’t offer us much new information because it increases our sample to a still-insignificant four districts. I don’t, however, want to get lost in the weeds of statistical extrapolation here. Rather, it is evident that Democrats are making gains from a very weak 2016 showing, even if uncertainty about the exact nationwide gain remains. The pattern in 2017 special elections has been Democratic overperformance, whether or not it is (yet) a “done deal.” Even outside House elections in tiny state assembly districts this has remained true.

Of course, measuring uncertainty can be helpful in gauging expectations for remaining special elections and actual midterms in 2018. Accounting for the small sample size, we could expect the real “democratic wave” to be anywhere from a 5.7 to 24 percentage point shift towards Democrats, 80% of the time. The bottom end of that interval matches what we see in the pro-Democrat shift in polls of the generic House ballot, which has moved five percent from where it stood on November 8th 2016. Using a 95% confidence interval, we see the possible “wave” could even be pro-Republican. That’s just how uncertain this all is right now.

Nevertheless, I find it hard to entertain the idea that Republicans could gain House seats in 2018, at least in the current environment. The above election results point towards a Democratic resurgence, as do polls and history. In past midterms, the incumbent party has lost an average of 26 seats per election. That’s not too far off from my math, which says that a 5.7 percentage point national uniform swing towards Democrats would give them 29 currently-GOP-held seats in the House, for a total of 219 (a majority). A 24 percentage point shift (which is almost impossible in most political environments) would give Democrats an enormous and unrealistic 328 of 435 house seats.

All of this news gets worse for Republicans when we consider that incumbent parties usually lose support over time, and I haven’t even talked about the president’s poor approval rating or the Republican’s toxic connection to healthcare policy in this post. All in all, it’s a bad picture for the GOP. After this is all over, they may even have preferred being body slammed by Greg Gianforte.

Ultimately, only time will answer our question of how big the Democrats will win in 2018. But, we don’t have to wait long to get more suggestions of how next year will play out. The runoff rounds of the special elections in California’s 39th and Georgia’s 6th district are less than a month away. If Montana is any indication of the future — and we should suspect it will be — we could be seeing more and more talk of 2018 Democratic pickups very shortly.

… . .

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