Democrats need to win 24 congressional seats in 2018 to take back the House. Despite extreme GOP gerrymandering of congressional districts in many states (the U.S. Supreme Court may have something to say about this next year), there are a number of opportunities that make this math possible.

There are 23 congressional districts represented by Republicans won by Hillary Clinton in 2016, and the demographic makeup of these districts are important after Tuesday’s off-year election results. As Daily Kos Elections analyzed earlier this year, These 23 Republicans hold congressional districts that voted for Hillary Clinton:

Daily Kos Elections recently completed calculating the 2016 presidential election results by congressional district. With ticket-splitting rates at historic lows, and presidential results highly correlated with congressional results, these numbers serve as a strong predictor of future House election outcomes. Consequently, as Democrats look to gain the 24 seats necessary to obtain a House majority, the 23 Republican-held congressional districts that voted for Hillary Clinton are a logical place to start.


[M]ost of these districts are located in upscale suburbs, particularly in Sun Belt states like California and Texas. Several of these seats have substantial Latino populations, while most also have many highly educated white voters who long leaned Republican before they revolted against Donald Trump. White voters have strongly polarized by education level in recent elections, with those holding a college degree increasingly voting Democratic at much higher rates than those who lack a four-year degree. If that trend persists, Trump could remain very unpopular in these suburban districts, giving Democrats an opening downballot.

These are precisely the college-educated suburban voters who revolted against “Trumpism” in Tuesday’s election. Suburbs Rebel Against Trump, Threatening Republicans in Congress:

The American suburbs appear to be in revolt against President Trump after a muscular coalition of college-educated voters and racial and ethnic minorities dealt the Republican Party a thumping rejection on Tuesday and propelled a diverse class of Democrats into office.

From the tax-obsessed suburbs of New York City to high-tech neighborhoods outside Seattle to the sprawling, polyglot developments of Fairfax and Prince William County, Va., voters shunned Republicans up and down the ballot in off-year elections. Leaders in both parties said the elections were an unmistakable alarm bell for Republicans ahead of the 2018 campaign, when the party’s grip on the House of Representatives may hinge on the socially moderate, multiethnic communities near major cities.

“Voters are taking their anger out at the president, and the only way they can do that is by going after Republicans on the ballot,” said Representative Charlie Dent, Republican of Pennsylvania.

The Democrats’ gains signaled deep alienation from the Republican Party among the sort of upscale moderates who were once central to their coalition.

* * *

Even in the Deep South, Georgia Democrats captured two State House seats where they previously had not even fielded candidates while snatching a State Senate seat in Buckhead, an upscale area of Atlanta.

This is the first group of House seats on which to concentrate. The second group emerging is a substantial number of retirements or House members running for other offices. The power of incumbency is the single greatest factor in retaining a House seat. An open congressional seat presents uncertainty and opportunity, even in districts which have been gerrymandered to be “bulletproof” GOP districts. Much of that advantage is tied to a particular incumbent, not a generic Republican.

Congressional Republicans on Wednesday were bracing for a new wave of retirements just one day after another pair of veteran House members, Representative Frank A. LoBiondo of New Jersey and Representative Ted Poe of Texas, declared they would not seek re-election. Already, 29 House Republicans have said they will not run again [Rep. Martha McSally running for the Senate would make 30], while just seven Democrats have announced plans to retire. [Democratic Rep. Kyrsten Sinema is running for the Senate].

Rep. Charlie Dent, channeling the exasperation of his colleagues, suggested an exodus might be imminent. “Do they really want to go through another year of this?” said Mr. Dent, a leader of his caucus’s moderate wing, who has announced he will not run again.

So this second group of open seats currently held by the GOP could grow exponentially in coming months if Rep. Dent’s prediction is correct.

There are 23 GOP districts won by Clinton and another 29 open districts due to Republican retirements (and that number is expected to grow). There are 40 seats currently held by Republicans where Donald Trump did not get to 50 percent of the vote in 2016. These 40 Republicans hold congressional seats where Donald Trump took less than 50 percent (17 additional seats that Donald Trump won with under 50 percent of the vote to the 23 GOP districts won by Hillary Clinton).

[S]ome of the most competitive House races of the 2018 midterms will take place in the two states that held elections on Tuesday. In New Jersey, Republicans will struggle to retain Mr. LoBiondo’s seat and must protect such imperiled incumbents as Leonard Lance, Tom MacArthur and Rodney Frelinghuysen. In Virginia, the district of Representative Barbara Comstock, a Republican, went 56 percent to 43 percent for Lt. Gov. Ralph S. Northam, the Democrats’ triumphant candidate for governor. Mr. Northam also captured 51 percent of the votes in the district of Representative Scott Taylor, a freshman Republican from Virginia Beach.

In the Senate, too, Democrats are seeking to expand the map, despite facing a narrow path to a majority. Democrats have 23 seats up for election to defend along with the 2 independents who caucus with them. Republicans have only 8 seats up for election in 2018. Two of those GOP seats, Dean Heller in Nevada and the seat being vacated by Jeff Flake are currently in play.

Democratic Party leaders gleefully predicted that the Senate, where Republicans hold a two-seat majority, might now be in play, and they said their fund-raising and candidate recruitment would take off going into the new year.

“We’ll get a lot of candidates who are going to want to run, and I think for donors who have been on the sidelines, dispirited for the last year, I’m telling you, people are jazzed up,” said Gov. Terry McAuliffe of Virginia, the ever-upbeat former national Democratic Party chairman.

To many Democrats and some Republicans, Tuesday’s results recalled the last time an unpopular Republican was in the White House and voters vented their frustrations on a Republican-held Congress. In 2005, Democrats rolled to victory in Virginia and New Jersey, presaging an electoral wave in 2006 and inspiring throngs of Democrats to run for office in difficult districts.

* * *

County-level results captured the dizzying scale of the lurch away from Republicans: In Virginia, Mr. Northam captured outer Washington suburbs, including Prince William and Loudoun Counties, by 20 percentage points or more, where other Democrats prevailed by single digits in the recent past. He won Virginia Beach, an area Mr. Trump carried last year, by five percentage points.

In New Jersey, Mr. Murphy carried the densely populated New York and Philadelphia suburbs by staggering margins, including counties that broke for Gov. Chris Christie, a Republican, eight years ago. And in Delaware County, Pa., long home to a fearsome Republican machine, Democrats won seats on the county council for the first time since the 1970s thanks to a local campaign that featured yard signs that got straight to the point: “Vote Nov. 7th Against Trump.”

Former Gov. Robert F. McDonnell, the last Republican to win a major office in Virginia, said the enthusiasm of liberal voters simply overwhelmed his party.

“The enthusiastic left showed up tonight in big numbers,” he said, “and really determined the outcome of the election.”