How Conservative/Liberal is Each Member of Congress? It Partially Depends on Where You Look and Who You Ask

As ubiquitous as the partisan contests are in politics and the punditry surrounding it, so too are the constant ideological struggles between conservatism and liberalism. Time and time again, we hear the Republican/Democrat and conservative/liberal dichotomies to the point that they seem interchangeable (and as talked about before, partisanship and ideology are not the exact same thing and people can have different conceptions of what conservative/liberal really means).

But how do we know just how conservative or liberal a legislator is? Can we definitively know this?

Yes. And no.

There are general depictions of how much certain legislators lean to one side or the other, but these also depend on where you look and who you ask. Where someone is on the political spectrum often shapes the perception of someone’s ideology. Staunchly conservative or liberal legislators and voters are usually going to see the other side as too extreme no matter how ideological they are, but they’ll also see their fellow conservatives or liberals that are more towards the center as “fake.” You may have heard them referred to as RINOs and DINOs, respectively — “Republicans-in-Name-Only” and “Democrats-in-Name-Only.” These are pejorative terms that are used to deem less ideological conservatives and liberals as not sufficiently conservative or liberal by those Republicans and Democrats who are more staunchly ideological.

There are, however, some more reliable statistical measures that we can use, although how they are calculated and interpreted can differ between who makes them. There are a variety of ways to look at this topic that help give a good sense of where legislators lean ideologically. We will take a look at some of those ways below.


DW-NOMINATE scores can be calculated along two dimensions. The first is simply by how liberal or conservative they are. The second is by a single issue or broad group of issues.¹ Below is an example of such a spatial map, where the ideology of U.S. Senators in the new Congress in relation to each other are placed based on their economic and social views. Those more to the right are more economically conservative and those more to the left are more economically liberal. Those higher up are more socially conservative and those further below are more socially liberal. As you can see here, their DW-NOMINATE scores can differ quite a bit on different dimensions. The closer dots on the map are to each other, the more similar their ideological leanings.

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Source: Voteview. “Congress view.”

DW-NOMINATE scores can also be depicted as a trend over time and numerically. An example is below. The chart below shows how ideological the parties have been on civil rights/social issues/regional issues over time in relation to each other. It also accounts for the regional factions of each party, which — while it still has some noticeable effects today — used to make an enormous difference in ideological leanings. Negative numbers in DW-NOMINATE scores indicate more liberal views, while positive numbers indicate more conservative views. (Negative and positive do not indicate value judgments. Neither is “bad” or “good” per se. They are just used to make a clear dividing line between conservative and liberal.)

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Source: Voteview Blog. “114th Congress.”

GovTrack Report Cards

On these report cards are the following categories for each member: bills cosponsored, bills introduced, bills out of committee, committee positions, cosponsors joining their bills, government transparency, ideology score, joining bipartisan bills, laws enacted, leadership score, missed votes, powerful cosponsors, working with the other chamber, and writing bipartisan bills. That probably seems overwhelming, but luckily GovTrack has already done all that work. You can look at the overarching 2018 report card here. Within each category are the subcategories of how it compares to legislators serving at least a certain length of time, all members of their party within their chamber (House or Senate), and their chamber overall.

For this article, we are mostly just concerned about their ideology score. Their ideology is compared along the aforementioned subcategories, and you can also see the percentile that they rank in each subcategory. For example, if it is measuring how liberal a member of Congress is and their ideology ranks at the 65th percentile among all Senators, that member of Congress is more liberal than 65% of the entire Senate chamber.

Interest Group Ratings

Some caution should be heeded when using interest group ratings, however. Because interest groups are often very narrow in their issue area they are active in, there is some chance that that politician’s ideological view on that particular issue differs from their overall ideology. Even politicians who lean solidly conservative or liberal can have a view or set of views on the opposite side of the political spectrum. Secondly, interest groups obviously a vested interest. What they perceive as too weak of support in an issue area doesn’t mean that they are “correct” in assessing a politician’s ideology.

Using Partisanship to Estimate Ideology

There are plenty of sources that track voting records of members, such as the aforementioned Voteview. A very consistent voting record for one’s party indicates that they clearly lean toward one side of the ideological spectrum, although it can miss some nuance. U.S. Senator Bernie Sanders, for example, is more liberal than a lot of Democrats, but there are Democrats that vote Democratic about as consistently — if not more so — than Sanders (Sanders caucuses with Democrats even though he is nominally independent). Likewise, U.S. Representative Liz Cheney is one of the more conservative Republicans, but there are plenty of Republicans that are similarly united with their party even if they are less conservative.

Thus, one should be careful using partisanship — how consistently one votes Republican or Democratic — in determining how ideological a politician is. It does, however, usually give a decent sense of what someone’s ideology is.

This is not a comprehensive list of ways you can look at measuring ideology and the sources that have them. This is meant to give a few tools through which to get a better understanding of just how ideology is analyzed. It also somewhat harkens back to the earlier article of what it means to be conservative/liberal in that ideology is more than just one dimension. The media may often only make cursory note of general ideology, but there can be some stark differences in economic/social views and within singular issues. Hopefully, this article helped give a more in-depth look at how to determine the ideology of members of Congress.

  1. Voteview. “About us.” (accessed January 30, 2019).

Written by

Senior Page Editor - Sayfie Review, Assistant Staff Writer - Ballotpedia (my views do not express those of my employers), M.A. in Political Science

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