This year, Americans elected 35 of the 100 members of the United States Senate and all 435 members of the United States House of Representatives, substantially altering the composition of Congress in what was largely the first national referendum on Donald Trump’s presidency. In the Senate, Republicans increased their majority by two seats to establish a new 53-47 advantage, while in the House, Democrats gained forty seats to retake the chamber by a 235-200 margin.

2018 United States Senate Elections

Democratic Hold (22)
Democratic Gain (2)
Republican Hold (7)
Republican Gain (4)

The 33 seats in Class I of the United States Senate were up this year, with an additional two special elections for Class II seats in Minnesota and Mississippi (represented by rectangles). Due to the staggered nature of Senate election cycles, Democrats found themselves largely playing defense this year, with 26 Democratic incumbents (a majority of Senate Democrats) but only nine Republican incumbents facing reelection. Democratic candidates may have viewed this situation as a blessing or a curse, as the party had little room for expansion but would much rather be defending its incumbents in a favorable environment than in any other.

Ten of the Democratic incumbents facing reelection hailed from states Donald Trump won in 2016, and four of them fell to Republican challengers – Senator Heidi Heitkamp (D) of North Dakota was defeated by Congressman Kevin Cramer (R), Senator Claire McCaskill (D) of Missouri was defeated by state Attorney General Josh Hawley (R), Senator Joe Donnelly (D) of Indiana was defeated by businessman Mike Braun (R), and Senator Bill Nelson (D) of Florida was defeated by Governor Rick Scott (R).

These seats were the four deemed by Democrats to be most vulnerable, and the results in none but Florida were even mildly surprising – most prognosticators expected Nelson, a three-term incumbent in a state Trump only won by 1.2% in 2016, to hang on. Indeed, Florida’s election was by far the closest of the 35 Senate races, with Scott prevailing by only 0.12% after two tumultuous recounts reminiscent of the 2000 disaster.

In six Trump states, Democratic incumbents hung on, with Bob Casey of Pennsylvania, Joe Manchin of West Virginia, Sherrod Brown of Ohio, Debbie Stabenow of Michigan, Tammy Baldwin of Wisconsin, and Jon Tester of Montana each winning another term. Other notable Democratic victories occurred in Minnesota, where Tina Smith was elected to a full term after her appointment in early 2018 to succeed the outgoing Al Franken, and New Jersey, where Bob Menendez was reelected despite a recent corruption scandal.

Democrats also made two gains – Congresswoman Jacky Rosen (D) defeated incumbent Senator Dean Heller (R) in Nevada, while Congresswoman Kyrsten Sinema (D) bested Congresswoman Martha McSally (R) in Arizona for the open seat of retiring Senator Jeff Flake (R). Heller was the only GOP incumbent from a state Hillary Clinton won in 2016, further suggesting an increase in national political polarization.

The GOP further defended three seats initially deemed competitive – Senator Ted Cruz (R) narrowly survived a spirited challenge from Congressman Beto O’Rourke (D) in Texas, while Congresswoman Marsha Blackburn (R) defeated former Governor Phil Bredesen (D) in Tennessee for the open seat of retiring Senator Bob Corker (R). And on November 27, Senator Cindy Hyde-Smith (R), appointed in early 2018 after the resignation of Senator Thad Cochran, won a full term in a runoff against former Agriculture Secretary Mike Espy (D) term despite numerous race-related controversies.

Notably, only three incumbent Senators retired this year – Republicans Jeff Flake of Arizona and Bob Corker of Tennessee both opted not to seek reelection after clashing frequently with President Trump, while Senate President pro tempore Orrin Hatch of Utah, the longest-serving Republican in Senate history, decided to retire after seven terms in the chamber. Hatch was replaced by 2012 GOP presidential nominee and former Massachusetts Governor Mitt Romney, who may or may not decide to continue the legacies of Flake and Corker by checking President Trump.

Republicans may suggest their net gain of two seats refutes claims of a blue wave, with Americans opting for a split decision of GOP control in the Senate and Democratic control in the House. This theory, however, ignores the context of the 2018 elections – Democrats faced the least favorable Senate map in a century but nonetheless prevailed in the national popular vote by a massive 58%-40% margin, garnering nearly 50 million votes nationwide while Republican candidates won only 34 million. Indeed Democrats succeeded in 69% of the 35 Senate elections this year, winning 24 seats compared to Republicans’ 11.

The following map displays the proportion of votes won by the winning candidate in each Senate election this year:

And the following map displays the partisan composition of each state’s delegation to the United States Senate in the upcoming 116th Congress:

Two Republicans (22)
Two Democrats (19)
Split Delegation (9)

2018 United States House of Representatives Elections

Democratic Hold (192)
Democratic Gain (43)
Republican Hold (197)
Republican Gain (3)

          Unlike the Senate, the House of Representatives saw a truly national election this year, with all 435 seats in the chamber up for grabs. Democrats gained a net total of forty seats, the party’s largest set of pickups since the post-Watergate midterms of 1974. Moreover, Democrats won the national popular vote by a 53%-45% margin, the largest popular vote advantage of either party since Democrats last won the House in 2008.

Democratic pickups were overwhelmingly concentrated in urban and suburban areas, with almost all of the party’s gains occurring in or around the nation’s largest cities. Indeed, Democrats gained eleven seats in the Northeast Megalopolis stretching from New York City to Washington, D.C. and an additional five seats in the Los Angeles metropolitan area. Republican gains, meanwhile, were confined to three seats in the Midwest – the party gained two rural seats in Minnesota vacated by retiring Democratic incumbents and one western Pennsylvania seat made substantially more Republican by court-mandated redistricting last year (the Democratic incumbent in that seat, Conor Lamb, won another term by defeating incumbent Republican Keith Rothfus in a neighboring district).

The 116th Congress will the most diverse in history, although diversity will largely be concentrated on one side – all but one of the incoming Republicans are white men, while a majority of the incoming Democrats are not. Moreover, the new Congress will feature its first Native American women (Sharice Davids of KS-03 and Debra Haaland of NM-01) and its first Muslim women (Rashida Tlaib of MI-13 and Ilhan Omar of MN-05).

The following map displays the proportion of votes won by the winning candidate in each House election this year:

And the following map displays the partisan composition of each state’s delegation to the United States House of Representatives in the 116th Congress:

Republican Majority (26)
Democratic Majority (22)
Split Delegation (2)

          Although Democrats now have a majority in the House, Republicans still control a majority of state delegations, epitomizing the increasing concentration of Democratic support in the urban and suburban areas of large, predominantly coastal states.

2018 Congressional Elections in North Carolina

Republican Hold (10)
Democratic Hold (3)

          Neither of North Carolina’s Senate seats had elections this year, but all thirteen House seats did. One GOP incumbent, Walter Jones of NC-03, ran unopposed.

Although Democrats won the popular vote in the twelve contested races by 131,061 votes (a 51%-47% margin), Republicans maintain a 10-3 advantage (77%-33%) in the state’s House delegation due to partisan gerrymandering. Indeed, federal judges have already struck down the state’s congressional map as unconstitutional, but the ruling occurred too late for new districts to be drawn this year. Assuming the ruling stands, new districts will be drawn by either the General Assembly or a court-appointed special master ahead of the 2020 elections. A nonpartisan map would likely result in a 7-6 House delegation, with either party able to win a majority of the congressional seats.

The following map displays the proportion of the vote garnered by the winning candidate in each congressional district:

While Walter Jones was unopposed in NC-03 and thus won all votes cast in his district, none of the remaining nine Republican winners prevailed with more than 60% in their respective races. The three reelected Democratic incumbents, meanwhile, each won at least 69% of votes in their districts. This indicates that the GOP legislators who drew the map packed as many Democratic voters as possible into few districts so Republican majorities could be spread throughout the remaining districts.

The following map displays which party’s congressional candidates collectively won more votes in each North Carolina county:

All Republican counties in the map above are represented by a Republican member of Congress, while twelve Democratic counties are not represented by a Democrat. This indicates that Republican legislators split many of the state’s Democratic strongholds between multiple districts to dilute Democratic strength – Fayetteville was split between NC-08 and NC-09, the Greensboro was split between NC-06 and NC-13, and Asheville was split between NC-10 and NC-11. All three of these cities are the proper size to fit within one district and could elect a Democratic member of Congress if not divided, but gerrymandering ensured GOP candidates would maintain control.

The following map displays the shift in support for each party in each congressional district from 2016 to 2018:

Republicans improved upon their 2016 performances slightly in NC-01 because of lower African American turnout relative to presidential election years and substantially in NC-03 because GOP incumbent Walter Jones ran unopposed. In the other eleven districts, meanwhile, Democrats improved upon their 2016 performances, generally by a margin of 5% to 10%.

The district with the highest Democratic swing (over 16%) was the only one in which the incumbent was not reelected – in NC-09, Republican challenger Mark Harris bested incumbent Robert Pittenger in the GOP primary and appeared to defeat Democrat Dan McCready in the general election by a mere 905 votes.

The final outcome in NC-09, however, is yet to be determined. Evidence of massive election fraud in Bladen and Robeson counties has emerged in recent weeks, with the State Board of Elections refusing to certify the election result and likely seeking to call a new election for the district altogether next year. A sample of our coverage of the scandal:

November 30 (Thomas Mills) –
November 30 (Kirk Kovach) –
December 3 (Thomas Mills) –
December 5 (Thomas Mills) –
December 6 (Thomas Mills) –
December 6 (Kirk Kovach) –
December 7 (Thomas Mills) –
December 7 (Kirk Kovach) –


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