A History of RCP Polls, Senate Races

Although my blog is about American history, I’m covering some history that is a bit more recent than most, indeed, most actors involved remain in the present. RealClearPolitics is quite simply the best outlet to find information and political perspectives. Its polling coverage is second to none and I give the website multiple checks a day (I wasn’t paid to write this). With the 2018 midterms on Tuesday, I grew curious to see what was possible on outcomes for the Senate in 2018. For this humble (okay, not too humble, I’m posting it) and amateur study, I am only counting races that RCP has labeled “tossups”, and the reason for this is explained in my findings section. For the raw data on the Senate race outcomes and RCP averages, here’s the data from the past five Senate cycles.


Alaska, Stevens (Inc.) v. Begich – Democrat Gain

Projected: Begich +10.3

Actual: Begich +1.3

Bias: +9 D

Georgia, Chambliss (Inc.) v. Martin, Republican Hold

Projected: Chambliss +3.8

Actual: Chambliss +3

Bias: +0.8 R

Kentucky, McConnell (Inc.) v. Lunsford – Republican Hold

Projected: McConnell +5.7

Actual: McConnell +5.8

Bias: +0.1 D

Minnesota, Coleman (Inc.) v. Franken – Democrat Gain

Projected: Coleman +2.8

Actual (Upset): Franken +0.01

Bias: +2.81 R

New Hampshire, Sununu (Inc.) v. Shaheen, Democrat Gain

Projected: Shaheen +9.6

Actual: Shaheen +6.4

Bias: +3.2 D

North Carolina, Dole (Inc.) v. Hagan – Democrat Gain

Projected: Hagan +4.3

Actual: Hagan +8.5

Bias +4.2 R

Oregon, Smith (Inc.) v. Merkley – Democrat Gain

Projected: Merkley +5.3

Actual: Merkley +3.3

Bias: +2 D

Average Bias: +0.93 D

Upsets: 1

Democrats won 5 of 7 (71%) toss-ups.


California, Boxer (Inc.) v. Fiorina – Democrat Hold

Projected: Boxer +5

Actual: Boxer +9.8

Bias: +4.8 R

Colorado, Bennet (Inc.) v. Buck – Democrat Hold

Projected: Buck +3

Actual (Upset): Bennet +0.9

Bias: +3.9 R

Illinois, Giannoulias v. Kirk – Republican Gain

Projected: Kirk +3.3

Actual: Kirk +1.9

Bias:  +1.4 R

Nevada, Reid (Inc.) v. Angle – Democrat Hold

Projected: Angle +2.7

Actual (Upset): Reid +5.6

Bias: +8.3 R

Pennsylvania, Sestak v. Toomey – Republican Gain

Projected: Toomey +4.5

Actual: Toomey +2

Bias: +2.5 R

Washington, Murray (Inc.) v. Rossi – Democrat Hold

Projected: Murray +0.3

Actual: Murray +3.8

Bias: +3.5 R

West Virginia, Manchin (Inc.) v. Raese – Democrat Hold

Projected: Manchin +4.5

Actual: Manchin +10.1

Bias: +5.6 R

Average Bias: +4.28 R

Democrats won 5 of 7 (71%) of toss-ups.

Upsets: 2


Indiana, Donnelly v. Mourdock – Democrat Gain

Projected: Donnelly +1.5

Actual: Donnelly +5.7

Bias: +4.2 R

Massachusetts, Brown (Inc.) v. Warren – Democrat Gain

Projected: Warren +3

Actual: Warren +7.5

Bias: +4.5 R

Montana, Tester (Inc.) v. Rehberg – Democrat Hold

Projected: Rehberg +0.4

Actual: Tester +3.7

Bias: +4.1 R

Nevada, Heller (Inc.) v. Berkley – Republican Hold

Projected: Heller +4

Actual: Heller +1.2

Bias: +2.8 R

North Dakota, Heitkamp v. Berg – Democrat Hold

Projected: Berg +5.7

Actual: Heitkamp +0.9

Bias: +6.6 R

Virginia, Kaine v. Allen – Democrat Hold

Projected: Kaine +1.8

Actual: Kaine +5.9

Bias: +4.1 R

Wisconsin, Baldwin v. Thompson – Democrat Hold

Projected: Baldwin +2.2

Actual: Baldwin +5.5

Bias: +3.3 R

Average Bias: +4.23 R

Democrats won 6 of 7 (86%) toss-ups.

Upsets: 2


Alaska, Begich (Inc.) v. Sullivan – Republican Gain

Projected: Sullivan +2.4

Actual: Sullivan +2.2

Bias: +0.2 R

Colorado, Udall (Inc.) v. Gardner – Republican Gain

Projected: Gardner +2.5

Actual: Gardner +2.5

Bias: None!

Georgia, Perdue v. Nunn – Republican Hold

Projected: Perdue +3

Actual: Perdue +7.9

Bias: +4.9 D

Iowa, Braley v. Ernst  – Republican Gain

Projected: Ernst +2.3

Actual: Ernst +8.5

Bias: +6.3 D

Kansas, Roberts (Inc.) v. Orman – Republican Hold

Projected: Orman +0.8

Actual (Upset): Roberts +10.8

Bias: +11.6 I

New Hampshire, Shaheen (Inc.) v. Brown – Democrat Hold

Projected: Shaheen +0.8

Actual: Shaheen +3.2

Bias: + 2.4 R

North Carolina, Hagan (Inc.) v. Tillis – Republican Gain

Projected: Hagan +0.7

Actual (Upset): Tillis +1.7

Bias: +2.4 D

Average Bias: -3.23 R

Republicans won 6 of 7 (86%) of toss-ups.

Upsets: 2


Florida, Rubio (Inc.) v. Murphy – Republican Hold

Projected: Rubio +3.7

Actual: Rubio +7.7

Bias: +4 D

Indiana, Young v. Bayh – Republican Hold

Projected: Young +0.7

Actual: Young +9.7

Bias: +9 D

Missouri, Blunt (Inc.) v. Kander – Republican Hold

Projected: Blunt +1.3

Actual: Blunt +2.8

Bias: +1.5 D

Nevada, Cortez Masto v. Heck – Democrat Hold

Projected: Cortez Masto +1.8

Actual: Cortez Masto +2.4

Bias: +0.6 R

New Hampshire, Ayotte (Inc.) v. Hassan – Democrat Gain

Projected: Ayotte +1.5

Actual (Upset): Hassan +0.2

Bias: +1.7 R

North Carolina, Burr (Inc.) v. Ross – Republican Hold

Projected: Burr +2

Actual: Burr +5.7

Bias: +3.7 D

Pennsylvania, Toomey (Inc.) v. McGinty – Republican Hold

Projected: McGinty +2

Actual (Upset): Toomey +1.6

Bias: +3.6 D

Wisconsin, Johnson (Inc.) v. Feingold – Republican Hold

Projected: Feingold +2.7

Actual (Upset): Johnson +3.4

Bias: +6.1 D

Average Bias: +3.2 D

Upsets: 3

Republicans won 6 of 8 (75%) of toss-ups.

Now, the 2018 race as it stands as of Saturday:

Arizona – McSally v. Sinema

Projected: Sinema +0.7 (Democrat Gain)

Florida – Nelson (Inc.) v. Scott

Projected: Nelson +1.4 (Democrat Hold)

Indiana – Donnelly (Inc.) v. Braun

Projected: Donnelly +0.8 (Democrat Hold)

Missouri – McCaskill (Inc.) v. Hawley

Projected: Tie

Montana – Tester (Inc.) v. Rosendale

Projected: Tester +4.2 (Democrat Hold)

Nevada – Heller (Inc.) v. Rosen

Projected: Heller +1 (Republican Hold)

Based on the information I have accumulated, several findings:

  1. There hasn’t been a Senate race that has been labeled Lean Dem or Lean GOP by RCP that has gone to the other party in the past ten years, which is why I am not including those races here. The closest this came to happening was in 2014, when Republican Ed Gillespie came within a point of defeating Virginia Democratic Senator Mark Warner. For Republicans, this means Michigan’s John James and New Jersey’s Bob Hugin will stay in their states. For Democrats, it means your dreams of Beto will merely be so.
  2. The worst polling average error in Senate races was in the case of the 2014 Kansas Senate race. The polling averages indicated that Independent Greg Orman would win by 0.8 points. The outcome was incumbent Republican Pat Roberts won by 10.8 points.
  3. The polling for tossup Senate races was biased to the GOP on average in 2010 (4.28%) and in 2012 (4.23%). However, the average polling bias shifted to the Democrats in the 2014 (3.23%) and 2016 (3.2%) elections.
  4. Neither party has ever lost all races RCP labeled “toss ups” in a Senate election cycle.
  5. The highest RCP average a candidate for the Senate had while still losing was Rick Berg in North Dakota, he was on average 5.7 points ahead.
  6. Only the 2014 Colorado Senate race’s average RCP polling matched the actual outcome: Cory Gardner winning by 2.5%.
  7. Since 2010, there have been at least two upsets per cycle, defined by me as the result being different from polling averages.

And now…predictions!

  1. Neither party will win all toss-ups.
  2. The GOP will win a minimum of 1-2 of these races.
  3. Jon Tester will win reelection, despite Trump’s visit to Montana to boost Rosendale.
  4. Democrats Nelson, Donnelly, and McCaskill were blessed to have deeply flawed GOP candidates running against them in 2012. None of them have that benefit this year. Expect at least one of them to lose this year, and if the GOP has a surprisingly good midterm, all three are in the cards.
  5. There will be a minimum of 2 upsets in this election cycle.


Battle for the Senate 2008. RealClearPolitics.

Retrieved from https://www.realclearpolitics.com/epolls/2008/senate/2008_elections_senate_map.html

Battle for the Senate 2010. RealClearPolitics.

Retrieved from https://www.realclearpolitics.com/epolls/2010/senate/2010_elections_senate_map.html

Battle for the Senate 2012. RealClearPolitics.

Retrieved from https://www.realclearpolitics.com/epolls/2012/senate/2012_elections_senate_map.html

Battle for the Senate 2014. RealClearPolitics.

Retrieved from https://www.realclearpolitics.com/epolls/2014/senate/2014_elections_senate_map.html

Battle for the Senate 2016. RealClearPolitics.

Retrieved from https://www.realclearpolitics.com/epolls/2016/senate/2016_elections_senate_map.html

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