Just the Facts

Five Facts on Which Party Will Win Control of the Senate

By Emma Petasis
September 26, 2018 | Blog

Midterms are 41 days away and all eyes are on which party will control the House and the Senate.  Here are five facts on the race to control the Senate:

The Republican Party has held the majority in the Senate since 2015

Congress has convened 10 times since 2000. Over this period Republicans have held the majority in Congress’ upper chamber six times, while Democrats have been in the majority only four times.  All four periods of Democratic control came between 2007 and 2015, with Democrats controlling as many as 57 seats between 2009 and 2011.  However, Republicans were able to regain control of the Senate in 2015 and have held it since. Currently, Republicans have a 51-49 (including 2 Independents that caucus with Democrats) majority in the Senate.

Of the 35 Senate seats on the ballot this cycle, 26 are held by senators who caucus with the Democrats

These numbers are obviously very favorable for Republican chances of holding, and even expanding, their majority in the Senate. To make matters worse for Democrats, only one of the nine Republican-held seats that is up for election—Sen. Dean Heller’s seat in Nevada—is in a state that Hillary Clinton won in 2016.  In contrast, 10 Democratic incumbents are running for re-election in states won by President Trump.

FiveThirtyEight, a statistical analysis website, gives Republicans a 69.4% chance of maintaining their majority in the Senate

As of September 26, the FiveThirtyEight model predicted that Republicans would maintain their majority in the Senate.  The model predicts the most likely outcome to be a 50/50 split between the two parties, with Vice President Mike Pence as the deciding vote.  While the model clearly favors Republican chances of holding the majority, it also indicates a relatively low chance that Republicans gain a significant number of seats, despite the number of Democratic incumbents up for re-election.  For example, the model gives Republicans only a 6.6% chance of gaining three seats and a 4.1% chance of gaining four.  Conversely, it gives Democrats a 16.1% chance of actually gaining a seat.

As of September 26, the Cook Political Reporta non-partisan election analysis outlet, estimates that 8 Senate seats are toss-ups

Cook uses four different qualifiers to rate races: solid, likely, lean, or toss-up.  If a seat is solid Republican or Democrat, it is highly likely that it will be won by that party.  Conversely, if a seat is a toss-up, either party has a good chance of winning.  Currently, the eight toss-up elections are split evenly between the two parties, with Democrats and Republicans each defending four seats.  For Democrats, their most endangered incumbents are from Florida, Indiana, Missouri, and North Dakota.  Of these four races, Sen. Heidi Heitkamp (D-ND) appears to be in the most trouble, with RealClearPolitics giving her opponent, Kevin Cramer, an average advantage of 1.6% in the polls. On the other side of the aisle, Republicans’ most endangered incumbents are running in Nevada and Texas, while the party tries to defend seats in Arizona and Tennessee that opened due to retirement. According to the polls, Republicans are most likely to lose their seat in Arizona, as Democratic candidate Kyrsten Sinema currently has an average advantage of 2.5%.

Sabato’s Crystal Ball, an election handicapping website run by Larry Sabato, a professor at the University of Virginia, rates only six Senate races as toss-ups

This is good news for Republicans, as Sabato rates both the Tennessee and Texas races as lean Republican.  Both states have been conservative strongholds for decades, but solid Democratic candidates have put them in play.  In Tennessee, Democrat Phil Bredesen, who previously served as mayor of Nashville from 1991 to 1999 and as governor from 1993 to 2000, is challenging Republican Marsha Blackburn, who has served in the House of Representatives since 2002.  In Texas, U.S. Rep. Beto O’Rourke has given Democrats their best chance of winning a statewide election in decades, as he attempts to unseat Republican Ted Cruz.

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