Benchmark Model: GOP poised to lose the House

The first release of the Benchmark House of Representatives Model is now live.

We detail our methodology for calculating those numbers here. The following races are determined through a mathematical model and do not take into account candidate quality.

Nearly every race in this list, even the Likely Republican races, is competitive. Benchmark expects at least 10 percent of the Likely Republican races to go Democrat. There are likely to be surprising results on Election Day in this regard.

You may notice some interesting results and differences from other forecasters, particularly for CA-21 and PA-17.

• California’s 21st Congressional District: While most of our projections agree with many other predictive outlets, Benchmark rates CA-21 much more likely to flip than others do. For example, the Cook Report rates CA-21 Lean Republican — although The Crosstab (a math-based model like ours) also forecasts this race to go to the Democrat. This is the question in a potential wave election year: Are moderate Republicans who win in Democratic districts safe or not? The Benchmark Model suggests not.

• Pennsylvania’s 17th Congressional District: PA-17 is rated as a tossup, according to the Cook Report, but we can’t ignore certain historical statistics of the district even after its lines changed. Benchmark lists it as Lean Republican. The model could very well be underestimating the Democrats in this district.

We will periodically post updates to this model. In Benchmark’s first two predictions this year, the House Model was extremely close: only one point off in the AZ-08 election, and two points off in the PA-18 election.

The bottom line: Democrats are poised to re-take the House of Representatives, but the margin is razor thin. At a generic ballot of D+6.2, the chances are only slightly better than 50/50.

It is important to note that there has been an enthusiasm gap that the generic ballot has not captured. Democrats hold a huge advantage in enthusiasm that may lead to higher turnout in spite of the generic ballot.

For daily updates, follow @benchmarkpol on Twitter.