Do primary voters strategically vote in the opposition’s primary?

Posted on Categories Lubar Center, Marquette Law School Poll, PublicLeave a comment» on Do primary voters strategically vote in the opposition’s primary?

Periodically political enthusiasts express concern that members of a particular political party will conspire to swing the result of the opposing party’s primary election by strategically voting for a candidate who does not express the actual will of that party’s “real” voters. This form of bad-faith strategic voting is sometimes called party raiding.

Party raiding is only feasible in states with open primaries, and fear of it is sometimes used as a argument in favor closed primary systems, which only allow registered partisans to vote in their respective primaries.

Wisconsin is an open primary state. In fact, the state’s Election Commission maintains no records of party affiliation whatsoever. Every party’s primary contests share space on a single ballot. Voters choose their preferred party in the privacy of the voting booth. No state presents fewer barriers to strategic party raiding than Wisconsin.

Nonetheless, there is no evidence that this kind of voting behavior occurs at all in Wisconsin. As I mentioned, registered voters do not have the option to formally affiliate with a party in Wisconsin. We can, however, measure party identification through public opinion data.

I pooled the results of three Marquette Law School Polls preceding the 2016 presidential preference vote and three surveys preceding the 2018 partisan primary. The combined dataset includes 3,515 likely voters. Each respondent was asked if they planned to vote in either the Republican primary, the Democratic primary, or if they didn’t plan to vote at all. We also recorded answers from respondents who insisted they would vote in “both” primaries, even though this would result in a spoiled ballot if carried out.

Respondents were also asked if they “usually think of yourself as a Republican, a Democrat, or an Independent.” Those who answered “independent” were then asked, “Do you think of yourself as closer to the Republican Party or to the Democratic Party?” We consider those who answered affirmatively as “leaning” partisans.

Here is how each partisan group planned to vote in the upcoming primary.

Stated intentions of Wisconsin primary voters by party ID, data from 2016 and 2018
partyID Republican primary Democratic primary Won’t vote Both Don’t know Refused
Rep 89 2 5 1 3 0
Lean Rep 77 4 9 1 7 1
Ind 25 16 17 3 36 4
Lean Dem 7 75 8 1 9 1
Dem 2 89 5 1 3 0

An identical share (2%) of Republicans and Democrats planned to vote in the other party’s primary. Even if this tiny share of people were indeed “party raiding,” they cancelled each other out. But there is no good evidence suggesting they weren’t voting in good faith. In the following general elections the share of self-identified Democrats or Republicans voting for a nominee of the other party exceeded 2%, so it’s quite likely that some share of self-identified Democratic voters genuinely preferred one of the Republican primary candidates and vice versa.

Recent changes in one of the most polarized places in America

Posted on Categories Lubar Center, Milwaukee Area Project, PublicLeave a comment» on Recent changes in one of the most polarized places in America

More than a quarter of Wisconsin lives in Greater Milwaukee–the four counties of Milwaukee, Waukesha, Ozaukee, and Washington. While these places are inextricably linked economically, they are famously divided politically. Writing in 2014, Craig Gilbert observed that the Milwaukee metro area might be the most politically polarized of all major cities in America. Based on the 2012 election alone, it was certainly among the top few.1

Much political commentary and analysis since 2016 has focused on declining Republican margins2 in suburban areas. Citylab classified every Congressional district by density and found that Democrats in 2018 flipped the House of Representatives due to their suburban gains. They picked up 9 seats in “dense suburban” areas, 13 seats in “sparse suburban” districts, and 5 seats in places with a “rural-suburban mix.”3

Even though no seats flipped in Wisconsin, the state nonetheless saw many political changes. In fact, the median community changed its vote preference by 14% from Obama’s reelection in 2012 to Tony Evers’ election in 2018. The remainder of this post explores how the Trump era has affected partisanship in this most polarized part of Wisconsin.

A note on measurement

To control for the see-saw nature of politics, most of the statistics I present are the “relative margin,” which is the partisan vote minus the statewide lean. First, I calculate the area’s vote margin (% Democrat minus % Republican); then I subtract the statewide margin. For example, the City of Waukesha voted 42% for Evers and 56% for Walker, so its absolute margin is -14%. The state as a whole had a margin of +1%. So Waukesha’s relative margin is -15% because it voted 15% more Republican than the state as a whole.


Since 1990, the Greater Milwaukee Area combined has voted Democratic in 5 out of 7 Presidential elections and Republican in 7 out of 9 Gubernatorial races. In his first three elections, Scott Walker won the Milwaukee Area by 47,200; 44,900; and 47,900 votes, respectively. In 2018 he lost by 17,600 votes. Since Tony Evers only won statewide by 29,227 votes, you could say Walker’s deteriorating support in the Milwaukee area cost him the election.

So what changed? Let’s first examine the vote in three broad swathes of the Milwaukee Area which collectively hold 85% of the region’s population.

  1. The City of Milwaukee, home to 595,000 people or about 44% of the population.
  2. Milwaukee County’s 18 suburbs, home to 357,000 people–about 23% of the population.
  3. Waukesha County’s 38 suburbs, home to 401,000 residents, or about 30% of the total.

Each of these areas has followed a different trajectory over the last few decades.

Consider the pre-Trump era. From 1990 to 2014, the City of Milwaukee grew steadily more Democratic. By the 2010s, Democrats in Milwaukee were beating their statewide performance by more than 50 points. On the other extreme, Waukesha County grew steadily redder. In the early 1990s, it usually voted around 26 points more Republican than the rest of the state. By the 2012/2014 elections, this had increased to 40. The Milwaukee County suburbs began the ’90s around 7% more Republican than the state, but gradually moved closer to the state average.

The two elections of the Trump era suggest things have changed. In Milwaukee City support for Clinton was even higher relative to the state average than it was for Obama in 2012. Conversely, there was a slight decline in the Democrat’s relative performance between the governor’s race in 2014 and 2018.

The big changes happened in the suburbs. In 2012, the Milwaukee County suburbs voted 4% more Republican than the rest of the state. In 2016, they voted 11% more Democratic. The shift between gubernatorial races was smaller (1% more Republican in 2014 compared with 6% more Democratic in 2018) but similarly abrupt and consequential.

Waukesha County experienced a strikingly similar trend. In 2012 it voted 41 points more Republican than the state overall. In 2016 this fell to 26 points. Likewise, Waukesha voted 40% more Republican than the state in Walker’s 2014 reelection, but this fell to 35% in his 2018 defeat.

Pre-Trump vs Trump-era

To get a better sense of the overall shifts from the pre-Trump to the current Trump era of partisan politics, I generated two statistics. First, I calculated the average adjusted margin of the 2012 and 2014 elections for president and governor (left map). Then I found the same statistic for the following elections in 2016 and 2018 (middle map). The difference between these two numbers shows a durable shift toward the Democratic party across nearly all Milwaukee Area suburbs, but the size of this shift varies considerably (right map).