Left-right ideology of voters, congressmembers, and senators

These plots from John Sides reminded me of some graphs from our forthcoming Red State, Blue State book that display the distributions of voters, House members, and senators on a common scale:


These are estimated based on some survey questions where voters were asked their views on a number of issues that had also been voted on in Congress. As you can see, elected representatives are generally more extreme than voters.

Polarization in red, purple, and blue states

We also looked at these distributions among Republican, battleground, and Democratic states (categorized based on their presidential voting patterns in 2000 and 2004). Geographic polarization is strong, especially in the Senate:


Voters in Republican and Democratic states are slightly more conservative and liberal, respectively, on the issues. Elected representatives are more geographically polarized: winner-take-all elections generally magnify differences that are already there. In a strongly Democratic-leaning state, it is likely that both senators will be Democrats and will be on the left side of the political spectrum. Such a state will also typically have many strongly Democratic congressional districts. The reverse pattern holds in Republican states.

6 Responses to Left-right ideology of voters, congressmembers, and senators

  1. Carolyn Kay July 21, 2008 at 5:59 am #

    I’d rather see graphs that show legislators’ leanings based on their ACTIONS, not on what they say.

    What I want for America is what 60-80% of Americans want, on almost every issue. But what most of us want is never what is implemented by our legislators.

    Carolyn Kay

  2. Randy July 21, 2008 at 6:13 am #

    Absurd stuff…meaningless…the definitions and liberal, left, conservative and right are fabricated. Let us see the survey…what kinds of questions were asked…what were the possible ranges of answers…how were they identified as liberal or conservative…

    This is the kind of bastardization of statistics that ruins the science.

  3. Andrew July 21, 2008 at 9:19 pm #


    The legislators’ positions are estimated from their votes (i.e., their actions). It’s the voters’ positions that are estimated from their survey responses.


    The questions asked in the survey are given in the Notes section of our book. Beyond that, I don’t know why you have a problem with bastardization. . . .

  4. ctate July 22, 2008 at 4:18 pm #

    Hm, there’s one particular implication here that I find quite surprising. The graphs suggest that there are members of Congress — perhaps several of them — who are noticeably more liberal than any voters. Living as I do in Berkeley, I find it pretty unlikely that there are multiple legislators in office who are MORE liberal than my local community.

  5. Andrew July 22, 2008 at 7:27 pm #


    The distributions are scaled to be the same size. So the question is whether in a random sample of 435 Americans, you’d expect to see anyone further to the left than the leftmost congressmember. The answer to that appears to be no.

    Beyond this, remember that the ideologies are scaled based on actual votes. So if your far-left friends have extreme views on issues that don’t come up in Congress, they won’t show up in this analysis.

  6. bullfighter July 24, 2008 at 11:48 am #

    These observations are interesting, but I am not sure what we can learn from them. I see some problems with comparing highly scrutinized and carefully thought out views of full-time politicians and on-the-fly views of private citizens. Also, the electorates in “battleground states” and “Democratic states” appear very similarly distributed, but they elect vastly different politicians. How would you explain that? Is something mismeasured here?