Welcome to our Election Update for Wednesday, Sept. 12!

Less than two months remain until the big day, and Democrats are in their best position yet in our House forecast. Our “Classic” model gives the party a 5 in 6 chance (81.8 percent) of seizing the chamber from Republicans. We envision an average Democratic gain of 38 seats.

We’ve spent an inordinate amount of time trying to identify patterns in the House battlefield: Will Democrats continue to make inroads into well-educated suburbs? Will Republicans hold onto working-class bastions? But at the heart of it, districts can be lumped into four categories: those that voted for Republican presidential candidates in both 2012 (Mitt Romney) and 2016 (Donald Trump); those that voted for Democratic presidential candidates (Barack Obama and Hillary Clinton) in both of the last two cycles; those that voted for Romney but then flipped to Clinton; and those that voted for Obama but then flipped to Trump.

Most districts fall into one of the first two buckets, according to presidential election results broken down by congressional district, as calculated by Daily Kos Elections. But it is the 34 districts that split their tickets between 2012 and 2016 that are on the front line of this year’s midterms, since their loyalties are more likely to be up for grabs. So we used our forecast model to see which party has the upper hand in those races.

Which types of district are most competitive? How competitive FiveThirtyEight’s forecast thinks races are in four types of districts, categorized by who carried them in the 2012 and 2016 elections Solid D Likely D Lean D Toss-up Lean R Likely R Solid R Romney-Trump 3 2 5 7 14 44 132 Romney-Clinton 0 4 3 3 2 1 0 Obama-Trump 4 6 0 6 2 3 0 Obama-Clinton 184 4 1 2 2 1 0 Source: Daily Kos Elections

Twenty-one of the 34 seats are Obama-Trump districts. As of 10:15 a.m., Democrats had an average 61 percent chance of winning these seats this fall; the median race in this category was a “toss-up.” If the Republicans want to play offense this year, this is where they’ll have some of their only opportunities. Nine of the 21 districts in Obama-Trump territory are currently held by Democrats, and the party had an average 82 percent chance of holding onto those seats. The median Democratic-held Obama-Trump district was rated “likely Democratic.”

The other 12 Obama-Trump districts are good targets for the Democratic effort to pick up seats. These Republican-held districts are more evenly distributed in terms of probability, with three rated “likely Democratic,” one “lean Republican,” three “likely Republican” and five “toss-up.” They had an average 54 percent chance of being won by a Republican again, so these really are some of the most suspenseful House elections to watch this year.





FiveThirtyEight releases House forecast update

Only 13 seats nationwide are Romney-Clinton districts, and amazingly, none of the 13 is currently represented by a Democrat. These districts had an average 60 percent chance of going blue. Seven were rated as either “likely” or “lean” Democratic. Compare that with only three rated as “likely” or “lean” Republican; the median Romney-Clinton district was rated “lean Democratic.”

For all the debate over whether Democrats should focus their efforts on ancestrally blue turf (the Obama-Trump seats, in our framework) or emerging battlegrounds where Trump is a poor fit (the Romney-Clinton seats), our model showed both groupings were about equally competitive (Democrats had a 61 percent chance in the former and a 60 percent chance in the latter). However, Democrats have a built-in advantage in some races in Obama-Trump districts: incumbency. (Remember, all the Romney-Clinton seats are currently held by Republicans.) But if you narrow the analysis to only seats where Democrats have a chance to make gains, the Romney-Clinton districts are easier targets than Obama-Trump ones. For example, Democrats were favored to gain a seat in four of the Republican-held Obama-Trump districts, while Republicans were favored to maintain control in eight; in Romney-Clinton districts, Democrats were favored to flip 10 seats and Republicans to successfully defend three.

Wondering what Democrats’ and Republicans’ chances are in specific Obama-Trump and Romney-Clinton districts? We’ll dive into the individual races in an upcoming Election Update.