Why is Alexandria Ocasio-Cortez estimated to be a moderate by NOMINATE?

Jeff Lewis

June 25, 2019

Media coverage of newly elected New York Congresswoman Alexandria Ocasio-Cortez describes her as liberal or even “ultra-liberal” with good reason. For example, she supports the green new deal, reparations for slavery, and abolishing ICE — all positions associated with the left wing of the Democratic caucus. Curiously, more than 150 roll calls into the 116th Congress, her first-dimension NOMINATE score places her to the right of the majority of freshman Democrats. So, why does NOMINATE think Ocasio-Cortez is a moderate? This question is made all the more puzzling because NOMINATE ranks Lauren Underwood, Rashida Tlaib, and Ilhan Omar as the three most liberal of the new Democrats in the House which is consistent with the media coverage and public statements of those three members. In what follows, I identify the roll calls that pull Ocasio-Cortez’s NOMINATE location away from the locations of Underwood, Tlaib and Omar and explain why NOMINATE cannot, as yet, conclude that Ocasio-Cortez belongs among the left-wing members of the Democratic caucus.

As shown below, the reason is quite simple. Because there have been relatively few roll calls taken that divide the left wing of the Democratic caucus from the moderates, there have been few opportunities for freshman liberals to show their stripes. On the vast majority of votes, members located at Ocasio-Cortez’s moderate position and, for example, Omar’s liberal position are expected by NOMINATE to vote the same way. While there are votes on which Ocasio-Cortez joins other strong liberals in voting against the moderates in her party, there are a handful of votes on which Ocasio-Cortez has gone against nearly every other Democrat including Omar, Tlaib and Underwood and sided with (nearly) every Republican. While Congressional observers understand that votes like Ocasio-Cortez’s vote against the rules of the House are protest votes, NOMINATE does not. Rather, NOMINATE sees these as instances in which Ocasio-Cortez looks like a conservative and it adjusts her location to be more conservative accordingly.

In those cases in which a large number of liberal members join the Republicans in voting against the Democratic moderates, NOMINATE concludes that the vote did not strongly divide liberals and conservatives. Consequently, NOMINATE discounts those sorts of votes in determining members’ locations. However, when a member goes alone (or nearly so), in bucking her party, NOMINATE finds that to be highly informative about the member’s location (this is how NOMINATE is able to correctly infer that Susan Collins is a moderate). This is what leads Ocasio-Cortez to be placed in the middle.

Over time, we expect that the 116th Congress will hold more votes that sharply divide the progressive wing of the Democratic party from the Democratic moderates and Republicans, but until it does, Ocasio-Cortez’s willingness to protest alone will lead NOMINATE not to locate her among the Congress’s most liberal members.

Liberal rankings of freshman Democrats in the 116th House

Here we see that while most of the highest-profile new liberals in the Congress are at the top of NOMINATE’s ranking, Ocasio-Cortez is only estimated to be the 44th most liberal of the 56 new Democrats.

Rank Member NOMINATE 1st Dimension
1 UNDERWOOD, Lauren (IL-14) -0.913
2 OMAR, Ilhan (MN-5) -0.765
3 TLAIB, Rashida (MI-13) -0.723
4 HILL, Katie (CA-25) -0.650
5 GARCÍA, Jesús (IL-4) -0.647
6 GARCIA, Sylvia (TX-29) -0.643
7 PRESSLEY, Ayanna (MA-7) -0.627
8 ESCOBAR, Veronica (TX-16) -0.613
9 STANTON, Greg (AZ-9) -0.534
10 LEVIN, Mike (CA-49) -0.534
11 NEGUSE, Joseph (CO-2) -0.534
12 SHALALA, Donna (FL-27) -0.534
13 TRAHAN, Lori (MA-3) -0.534
14 LEVIN, Andy (MI-9) -0.534
15 HAALAND, Debra (NM-1) -0.534
16 PAPPAS, Chris (NH-1) -0.518
17 WEXTON, Jennifer (VA-10) -0.472
18 DEAN, Madeleine (PA-4) -0.471
19 FLETCHER, Elizabeth (TX-7) -0.463
20 CISNEROS, Gil (CA-39) -0.462
21 STEVENS, Haley (MI-11) -0.458
22 PORTER, Katie (CA-45) -0.439
23 ALLRED, Colin (TX-32) -0.424
24 COX, TJ (CA-21) -0.423
25 ROUDA, Harley (CA-48) -0.408
26 HARDER, Josh (CA-10) -0.399
27 MUCARSEL-POWELL, Debbie (FL-26) -0.390
28 HAYES, Jahana (CT-5) -0.344
29 KIM, Andy (NJ-3) -0.341
30 SCHRIER, Kim (WA-8) -0.330
31 HOULAHAN, Christina (PA-6) -0.328
32 FINKENAUER, Abby (IA-1) -0.295
33 CRAIG, Angela (MN-2) -0.289
34 AXNE, Cynthia (IA-3) -0.275
35 MALINOWSKI, Tomaz (NJ-7) -0.253
36 CROW, Jason (CO-6) -0.246
37 CASTEN, Sean (IL-6) -0.230
38 TRONE, David (MD-6) -0.229
39 SLOTKIN, Elissa (MI-8) -0.220
40 LEE, Susie (NV-3) -0.215
41 PHILLIPS, Dean (MN-3) -0.213
42 LURIA, Elaine (VA-2) -0.199
43 McBATH, Lucy (GA-6) -0.196
44 OCASIO-CORTEZ, Alexandria (NY-14) -0.193
45 DAVIDS, Sharice (KS-3) -0.175
46 SPANBERGER, Abigail (VA-7) -0.175
47 VAN DREW, Jefferson (NJ-2) -0.163
48 SHERRILL, Mikie (NJ-11) -0.161
49 HORN, Kendra (OK-5) -0.160
50 DELGADO, Antonio (NY-19) -0.146
51 TORRES SMALL, Xochitl (NM-2) -0.139
52 GOLDEN, Jared (ME-2) -0.134
53 McADAMS, Ben (UT-4) -0.129
54 BRINDISI, Anthony (NY-22) -0.120
55 ROSE, Max (NY-11) -0.116
56 CUNNINGHAM, Joe (SC-1) -0.107

Votes that moderate Ocasio-Cortez’s NOMINATE placement

The table below shows all of the votes on which Ocasio-Cortez is predicted by NOMINATE to have less than a 40 percent chance of casting a vote on the side that she did. The roll call numbers shown in the first column are also clickable links to the pages for those votes on Voteview. The votes are sorted by the probability that NOMINATE attaches to Ocasio-Cortez’s vote on each roll call. These votes tell us just about all we need to know about why Ocasio-Cortez is estimated to be a moderate by NOMINATE.

For example, on rollcall number 48, Ocasio-Cortez was the only Democrat to vote “nay” and only ten Republicans voted “Yea.” On that vote, liberal members such as Underwood, Tlaib, and Omar are predicted to vote “Yea” with near (certainty). Even at Ocasio-Cortez’s moderate NOMINATE position, NOMINATE only gives her “Nay” vote a 1.8 percent chance. All of these votes illustrate instances in which Ocasio-Cortez broke from her party including at least some or all of its left-wing. In order to accommodate these maverick votes, NOMINATE adjusts her position to reflect that she has on several occasions cast votes that are (otherwise) strongly consistent with being a conservative.

Ocasio-Cortez
Underwood/Tlaib/Omar
Rollcall Bill Description Vote Prob. Votes Avg. Prob.
48 HR648 Consolidated Appropriations Act, 2019 (On Passage) N 1.1 YYY 99.9
45 HJRES28 Making further continuing appropriations for fiscal year 2019, and for other purposes (On Passage) N 2.6 YYY 99.9
50 HJRES31 Making further continuing appropriations for the Department of Homeland Security for fiscal year 2019, and for other purposes (On Passage) N 3.4 YYY 99.9
228 NA On Approving the Journal N 7.9 YYY 98.8
57 HR769 Counterterrorism Advisory Board Act (On Motion to Suspend the Rules and Pass) N 17.7 NNY 30.8
72 HR840 On Agreeing to the Amendment N 18.2 NNY 38.5
6 HRES6 Adopting the Rules of the House of Representatives for the One Hundred Sixteenth Congress, and for other purposes (On Agreeing to Title I of the Resolution) N 21.4 YYY 98.4
86 HJRES31 Making further continuing appropriations for the Department of Homeland Security for fiscal year 2019, and for other purposes (On Agreeing to the Conference Report) N 21.9 NNY 35.9
56 HR449 Pathways to Improving Homeland Security at the Local Level Act (On Motion to Suspend the Rules and Pass) N 36.4 YYY 92.4

Few votes in the 116th House have divided liberal from moderate Democrats (through May 2019)

The following plot shows the probability that NOMINATE assigns to votes cast by Ocasio-Cortez against the average probability that it assigns to votes cast by Omar, Tlaib and Underwood on each rollcall in which Ocasio-Cortez, Omar, Tlaib, and Underwood all voted the same way. Here we see that on most of these votes, even with her moderate location, Ocasio-Cortez’s votes are well predicted by NOMINATE. Put another way, we find only a small number of votes for which moving Ocasio-Cortez to a similar location to Omar, Tlaib and Underwood would substantially increase the fit of Ocasio-Cortez’s votes. Thus, while her go-it-alone protest votes provide a strong impetus for NOMINATE to moderate Ocasio-Cortez’s location, the large number of votes on which she agrees with the other liberal Democrats provide little impetus for moving her position leftward.

Likelihood of Ocasio-Cortez’s votes by DW-NOMINATE position

Here we plot the likelihood (represented as the geometric mean probability of her vote choices) of Ocasio-Cortez’s votes being cast by a member located anywhere in the DW-NOMINATE space. Her actual estimated location, the one that maximizes the likelihood of her votes, is represented by the black dot. Note that the likelihood of her votes falls off rapidly as her location is shifted to the right while she can be moved along the edge of the space to the left with relatively less reduction in fit.