OZY’s Exclusive Election Model: Senate Looks Out of Reach for Democrats

OZY’s Exclusive Election Model: Senate Looks Out of Reach for Democrats

Sen. Dean Heller, R-Nev, speaks during a visit by Vice President Mike Pence at Nellis Air Force Base in Las Vegas Friday, Sept. 7, 2018.

SourceSteve Marcus/Las Vegas Sun/AP

Why you should care

Republicans have an equal chance — 90 percent — at keeping the Senate and losing the House.

In November’s midterm elections, Senate Republicans are defending only one state where Hillary Clinton won in 2016. And with this year’s political climate substantially favoring Democrats, that should mean Nevada Republican Dean Heller is a goner. And yet, the incumbent who’s wrapping up his first full term has hung strong in the polls — leading our election projection model to give him a coin flip’s 49.6 percent chance of victory.

The race is emblematic of the hardening political realities for Democrats in their quest to retake the Senate, which was never going to be easy. Our election forecasts, conducted exclusively with the consulting firm 0ptimus, this week show Republicans with a 91.2 percent chance of taking the Senate — the highest since we launched the model in September.

But Republicans face a mirror uphill climb for the House, where Democrats have an 89.2 percent chance of claiming control, an indication of the vastly different playing fields in the two chambers this year.

In partnership with the Republican technology and data firm 0ptimus, we crunched more than 100 factors that helped predict past elections, with extra weighting for unique aspects of this political year, to produce these forecasts. For more on how these numbers were derived, scroll down to the box below. For more exclusive election coverage, subscribe to our Midterms in a Minute newsletter.

This week saw the national picture improve slightly for Republicans, though Democrats continue to hold a 6.9 percentage point advantage. Despite the big-picture movement toward the GOP — a trend line that has continued for a month, coinciding with the fight over Brett Kavanaugh’s Supreme Court nomination — Democrats’ chances of taking the House improved. This was because of a series of individual race polls favoring the Democrats. OZY and 0ptimus now project Democrats to win 228 House seats, to 207 for Republicans, a one-seat improvement for Democrats since last week.

A trio of key races now have moved from toss-up to lean-Democrat status: Colorado’s 6th District, California’s 10th District (featured as part of our Ground Game coverage of bellwether seats) and New Jersey’s 11th District (where we profiled Democrat Mikie Sherrill earlier this year).

Meanwhile, in the Senate, the North Dakota race in recent weeks has shifted from a toss-up to a greater than 70 percent chance of victory for Republicans. The GOP has similar odds of holding Texas and Tennessee, where Republican Marsha Blackburn is starting to take control despite last week’s endorsement of Democrat Phil Bredesen by pop star Taylor Swift. To claim the majority, Democrats would need to win one of those three.

But Alex Alduncin, data scientist for 0ptimus, points out that nothing is set in stone. “If we had to pick one, the Senate side probably has a more fluid nature, since Democrats polling well in two to three key seats over the next few weeks could potentially even things out,” he says.

As part of our extensive on-the-ground coverage of races across the U.S. this year, OZY wanted to build a better product to analyze the national political picture — given the failure of such forecasts in the past. So we decided to team up with Washington-based 0ptimus, a Republican firm that developed an unbiased, nonpartisan prediction model to show its clients in both politics and finance where the winds appear to be blowing.

0ptimus’ data team created and tested countless models, crunching publicly available data against past results in House and Senate races. They take into account more than 100 variables, including past vote totals, generic ballot surveys of which party voters prefer in Congress, the unemployment rate, fundraising data and public polling. The firm developed an artificial intelligence system to “smartly” average together several models to produce the strongest prediction numbers for the 2018 elections, automatically testing against past elections to assess quality. You can read more about the 0ptimus methodology here.

Given the unique factors in 2018, we asked 0ptimus to tweak its calculations, adding weight to:

  • The number of small donations — a sign of energy for candidates from Trump to Alexandria Ocasio-Cortez.
  • Gender — women are doing exceptionally well this year, and we expect that trend to continue.
  • Trump’s approval rating — he hangs over the political and media scene with a heavier presence than past presidents.

Meanwhile, we asked 0ptimus to reduce the weight for:

  • Candidate ideology — its calculations rewarded more moderate candidates, while we think this election year is all about firing up the base.
  • Outside money — as OZY has reported, advertising is less persuasive coming from a super PAC than from a candidate.

Because 0ptimus averages several models, it agreed to introduce a new Bayesian model into the mix just for OZY that includes Trump’s approval, gender and unitemized donations while removing one that included ideology and independent expenditures. The result is the numbers we update for you each week.

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