{
  "alt": "Line chart by presidential election from 1992 to 2024 with four lines. The House whole-gap line falls from {fact:house_rms_1992} points in 1992 to {fact:house_rms_2024} points in 2024. The House line for variation inside a district is lower in every election, at {fact:house_rms_in_1992} points in 1992 and {fact:house_rms_in_2024} in 2024. The Senate lines are lower still in 2024, at {fact:senate_rms_2024} for the whole gap and {fact:senate_rms_in_2024} for variation inside a state.",
  "caption": "The solid lines are the whole gap and the dashed lines what remains after each district's or state's average gap is removed, so the distance between a solid and a dashed line is the shared shift. In 2024 the root mean square of the House gap is {fact:house_rms_2024} points and the part that varies inside districts is {fact:house_rms_in_2024} points; the Senate figures are {fact:senate_rms_2024} and {fact:senate_rms_in_2024}. The House lines use counties wholly inside one district.",
  "data": [
    {
      "n_units": 2348,
      "series": "House, whole gap",
      "value": 27.0063,
      "year": 1992
    },
    {
      "n_units": 2348,
      "series": "House, variation inside a district",
      "value": 9.1077,
      "year": 1992
    },
    {
      "n_units": 2329,
      "series": "House, whole gap",
      "value": 23.3958,
      "year": 1996
    },
    {
      "n_units": 2329,
      "series": "House, variation inside a district",
      "value": 7.26951,
      "year": 1996
    },
    {
      "n_units": 2190,
      "series": "House, whole gap",
      "value": 28.3597,
      "year": 2000
    },
    {
      "n_units": 2190,
      "series": "House, variation inside a district",
      "value": 7.13784,
      "year": 2000
    },
    {
      "n_units": 2078,
      "series": "House, whole gap",
      "value": 27.8448,
      "year": 2004
    },
    {
      "n_units": 2078,
      "series": "House, variation inside a district",
      "value": 7.38142,
      "year": 2004
    },
    {
      "n_units": 2280,
      "series": "House, whole gap",
      "value": 24.8421,
      "year": 2008
    },
    {
      "n_units": 2280,
      "series": "House, variation inside a district",
      "value": 7.37161,
      "year": 2008
    },
    {
      "n_units": 2229,
      "series": "House, whole gap",
      "value": 12.4924,
      "year": 2012
    },
    {
      "n_units": 2229,
      "series": "House, variation inside a district",
      "value": 4.98489,
      "year": 2012
    },
    {
      "n_units": 2037,
      "series": "House, whole gap",
      "value": 14.2825,
      "year": 2016
    },
    {
      "n_units": 2037,
      "series": "House, variation inside a district",
      "value": 6.01352,
      "year": 2016
    },
    {
      "n_units": 2445,
      "series": "House, whole gap",
      "value": 6.25173,
      "year": 2020
    },
    {
      "n_units": 2445,
      "series": "House, variation inside a district",
      "value": 2.64497,
      "year": 2020
    },
    {
      "n_units": 2277,
      "series": "House, whole gap",
      "value": 5.51989,
      "year": 2024
    },
    {
      "n_units": 2277,
      "series": "House, variation inside a district",
      "value": 2.26679,
      "year": 2024
    },
    {
      "n_units": 1823,
      "series": "Senate, whole gap",
      "value": 20.5385,
      "year": 1992
    },
    {
      "n_units": 1823,
      "series": "Senate, variation inside a state",
      "value": 8.0478,
      "year": 1992
    },
    {
      "n_units": 2288,
      "series": "Senate, whole gap",
      "value": 15.219,
      "year": 1996
    },
    {
      "n_units": 2288,
      "series": "Senate, variation inside a state",
      "value": 5.66789,
      "year": 1996
    },
    {
      "n_units": 1858,
      "series": "Senate, whole gap",
      "value": 18.5073,
      "year": 2000
    },
    {
      "n_units": 1858,
      "series": "Senate, variation inside a state",
      "value": 5.97935,
      "year": 2000
    },
    {
      "n_units": 2006,
      "series": "Senate, whole gap",
      "value": 22.6788,
      "year": 2004
    },
    {
      "n_units": 2006,
      "series": "Senate, variation inside a state",
      "value": 6.86254,
      "year": 2004
    },
    {
      "n_units": 2055,
      "series": "Senate, whole gap",
      "value": 16.013,
      "year": 2008
    },
    {
      "n_units": 2055,
      "series": "Senate, variation inside a state",
      "value": 6.62111,
      "year": 2008
    },
    {
      "n_units": 1843,
      "series": "Senate, whole gap",
      "value": 12.5714,
      "year": 2012
    },
    {
      "n_units": 1843,
      "series": "Senate, variation inside a state",
      "value": 4.45434,
      "year": 2012
    },
    {
      "n_units": 1989,
      "series": "Senate, whole gap",
      "value": 13.4092,
      "year": 2016
    },
    {
      "n_units": 1989,
      "series": "Senate, variation inside a state",
      "value": 8.00517,
      "year": 2016
    },
    {
      "n_units": 2212,
      "series": "Senate, whole gap",
      "value": 5.52847,
      "year": 2020
    },
    {
      "n_units": 2212,
      "series": "Senate, variation inside a state",
      "value": 2.98202,
      "year": 2020
    },
    {
      "n_units": 1749,
      "series": "Senate, whole gap",
      "value": 6.09471,
      "year": 2024
    },
    {
      "n_units": 1749,
      "series": "Senate, variation inside a state",
      "value": 2.51871,
      "year": 2024
    }
  ],
  "id": "gap_components",
  "notes": [
    "Full counts of votes, so the county series have no sampling interval.",
    "A root mean square is the square root of the vote-weighted mean of the squared gap, so large gaps count more than in an average of absolute gaps. Districts and states with one county in the sample are left out, and the part inside each unit is multiplied by n over n minus one for a unit of n counties, because a unit's own average absorbs part of its counties' deviations."
  ],
  "source": "County returns for President, U.S. House and U.S. Senate, 1992-2024 (Heideman 2026, with MIT Election Data and Science Lab presidential returns); full counts, unweighted",
  "spec": {
    "colors": {
      "House, variation inside a district": "cat1",
      "House, whole gap": "cat1",
      "Senate, variation inside a state": "cat2",
      "Senate, whole gap": "cat2"
    },
    "dashed": [
      "House, variation inside a district",
      "Senate, variation inside a state"
    ],
    "n": "n_units",
    "series": "series",
    "x": "year",
    "xDomain": [
      1990,
      2026
    ],
    "xLabel": "Presidential election",
    "xTicks": [
      1992,
      1996,
      2000,
      2004,
      2008,
      2012,
      2016,
      2020,
      2024
    ],
    "y": "value",
    "yDomain": [
      0,
      30
    ],
    "yFormat": {
      "digits": 0
    },
    "yLabel": "Root mean square gap (points of margin)"
  },
  "subtitle": "Vote-weighted root mean square of the down-ballot margin minus the presidential margin, in points of margin, and the part that varies among counties inside one district (House) or state (Senate), 1992 to 2024",
  "table": {
    "columns": [
      {
        "key": "series",
        "label": "Series"
      },
      {
        "key": "year",
        "label": "Election"
      },
      {
        "format": {
          "digits": 1
        },
        "key": "value",
        "label": "Root mean square (points)"
      },
      {
        "format": {
          "thousands": true
        },
        "key": "n_units",
        "label": "Counties"
      }
    ]
  },
  "title": "A shift shared by the counties of one district or state accounts for most of the gap between presidential and down-ballot margins",
  "type": "line",
  "width": "wide"
}