Supplementary materials

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Supplementary materials

A. Details on the party membership surveys used in the study.

The web-based survey of the PD’s enrolled members was carried out in 2013, immediately after the center-left coalition’s open primaries for selecting the Prime Ministerial candidate for the 2013 general election. The sample was drawn from the party membership lists and it included all PD members who provided their email address upon their enrolment (N=100,000). The web survey was available online from 25 March to 14 April 2013. At the end of 2011, the PD registered 763,783 members nationwide, and over the three weeks of the survey a total of 13,666 responses were collected (26 of which were by members living abroad). The respondents thus represent 1.8% of the overall PD membership and generate a response rate of 14%. The web-based survey of the LN’s enrolled members was conducted immediately after the party organized a closed primary election for selecting the party leader in December 2013. The questionnaire was sent electronically to a sample constituted by all LN members who provided their email address upon their enrolment. The web survey was available online from 10 February to 10 March 2014, and we collected a total of 5,147 responses. Unfortunately, since the survey was managed directly by the party central offices on the basis of a very strict overseeing procedure, we are not able to estimate the response rate.

Nevertheless, according to the LN website, in 2013 the LN declared an enrolment total of 12,000 members. Thus, we can estimate that our responses generate a population frame coverage of 42.8%.

However, given that the central offices of the party drew the sample and refused to divulge the sample size, we cannot estimate the response rate.

The web-based survey on M5S’s enrolled members was s realized a few months after M5S organized an online closed primary election for selecting parliamentary candidates for the 2013 general election. However, the sampling procedure was quite different because of constraints imposed by the party central offices. The party requested direct management of the survey by using snowball, non-probability sampling and by sending the survey to all but two its regional branches (Aosta Valley and Trentino, which are the smallest), which then sent out the questionnaire electronically to all the M5S members enrolled in each branch and who provided their email address upon their enrolment. The web survey was available online from 25 March to 14 April 2013 and we collected a total of 628 responses. It is not possible to precisely estimate the population frame coverage of our respondents, because the party did not release any information about its membership until the end of 2012 (N=31,612). If we take these membership figures at face value, we can estimate that the respondents generated a population frame coverage of 1.9%. We

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experienced similar problems in estimating the response rate, because the local branches refused to divulge any data about their members or the size of the sample.

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B. Descriptive analyses on the variables included in the study.

Table 1a: Descriptives

PD LN M5S

N MI

N MAX AVG SD N MI

N MAX AVG SD N MIN MAX AVG SD

Opinion on

primaries 11,855 0 1 0.73 0.44 4,303 0 1 0.64 0.48 476 0 1 0.74 0.44

Intra-party activity

h/w 12,63 1 6 2.46 1.35 4,806 1 6 2.63 1.52 549 1 6 3.05 1.55

Membership

duration 11,428 1 6 5.10 1.39 4,605 1 4 2.22 0.81 485 1 5 2.23 1.54

Gender 13,666 1 2 1.71 0.46 5,129 1 2 1.81 0.39 627 1 2 1.79 0.40

Education 13,666 1 4 3.36 0.68 5,129 1 4 3.09 0.71 627 1 4 3.03 0.69

Age 13,613 16 91 53.32 13.6

1 5,107 16 89 49.12 13.3

9 625 18 78 41.37 10.84 L/R self-placement 12,727 1 10 2.53 1.38 4,462 1 10 8.29 1.87 516 1 10 4.16 2.31

Source: Authors’ own elaboration.

Table 2a. Socio-demographic Profiles of Party Members

Party PD LN M5S

Gender Male 70.7 81.1 79.4

Female 29.3 19.9 20.6

Total (N) 13,666 5129 627

Age <35 13 16.6 30.9

>65 21.3 13.7 1.3

Mean 53.3 49.12 41.4

Total (N) 13,613 5,107 627

Education None/Elementary 0.7 1.1 1.0

Junior high 9.8 17.6 19.6

High school 42.3 51.9 54.9

Higher education 47.2 29.3 24.6

Total (N) 13,666 5,129 627

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C. Ordinal Regression Models

Table 3a: Determinants of Members’ Perceptions of Primary Elections: Partito Democratico

Predictor SE Odds ratio

Intra-party activism (ref. Cat.= Inactive)

Less than 2 h/w 0.04860 1.078

Between 2 and 5 h/w 0.05224 1.018

Between 5 and 10 h/w 0.06475 0.881°

Between 10 and 20 h/w 0.08706 0.959

More than 20 h/w 0.09713 0.615***

Membership duration 0.01462 0.991

Previous party membership (ref. cat. = no) 0.04225 0.653***

L/R ideological placement (1-10 scale) 0.01367 0.941***

Male 0.04137 1.196***

Age 0.00146 1.007***

Education (ref. cat. = elementary)

Middle school 0.23305 1.030

High school 0.22776 0.922

University 0.22797 0.987

N 10,642

AIC 26119

Nagelkerke R Square 0.012

*** p<0.001; **p<0.005; *p<0.010; °p<0.050

Note: Ordinal Regression Model. Dependent Variable = primary elections improved my overall evaluation of the party, 1=strongly disagree; 2= fairly disagree; 3= fairly agree; 4= strongly agree.

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Table 4a: Determinants of Members’ Perceptions of Primary Elections: Lega Nord

Predictor SE Odds

ratio Intra-party activism (ref. Cat. = Inactive)

Less than 2 h/w 0.0831

7 1.136

between 2 and 5 h/w 0.0843

5 1.416***

between 5 and 10 h/w 0.1054

0

1.279°

Between 10 and 20 h/w 0.1304

9 1.452*

More than 20 h/w 0.1251

9 1.414*

Membership duration (ref. cat. = between 2010 and 2013)

Between 2000 and 2010 0.0815

2 0.728***

Between 1990 and 2000 0.0920

7 0.590***

Before 1990 0.1532

7 0.526***

Previous party membership (ref. cat. = no) 0.0793

7 1.170°

L/R ideological placement (1-10 scale) 0.0164

1 1.066***

Male 0.0784

0 1.230*

Age 0.0024

5

1.004 Education (ref. cat. = elementary)

Middle school 0.3282

5

0.928

High school 0.3241

9 0.837

University 0.3270

9 0.750

N 3,818

AIC 10048

Nagelkerke R Square 0.012

*** p<0.001; **p<0.005; *p<0.010; °p<0.050

Note: Ordinal Regression Model. Dependent Variable = primary elections improved my overall evaluation of the party, 1=strongly disagree; 2=fairly disagree; 3= Fairly agree; 4=strongly agree.

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Table 5a: Determinants of Members’ Perceptions of Primary Elections: Movimento 5 Stelle

Predictor SE Odds ratio

Intra-party activism (ref. Cat.= Inactive)

Less than 2 h/w 0.32182 1.423

between 2 and 5 h/w 0.31010 1.890*

between 5 and 10 h/w 0.31257 2.003*

Between 10 and 20 h/w 0.36743 1.128

More than 20 h/w 0.40282 2.151°

Membership Duration 0.06834 0.982

Previous party membership (ref. cat. = no) 0.26044 0.727

L/R ideological placement (1-10 scale) 0.04301 0.968

Male 0.25255 1.423

Age 0.00927 1.007

Education (ref. cat. = elementary)

Middle school 1.20334 4.524

High school 1.18955 3.430

University 1.19892 2.991

N 383

AIC 960

Nagelkerke R Square 0.022

*** p<0.001; **p<0.005; *p<0.010; °p<0.050

Note: Ordinal Regression Model. Dependent Variable = primary elections improved my overall evaluation of the party, 1=Strongly disagree; 2= Fairly disagree; 3= fairly Agree; 4= Strongly Agree.