Thanks to Zach and Blogging Blue for the opportunity to guest blog. I’ll be discussing election analytics with a focus on Wisconsin politics.
As Blogging Blue readers know, in January Republicans will once again enjoy full control of Wisconsin state government, having retaken the State Senate earlier this month. The GOP will hold a 17-15 edge in the senate, likely to become 18-15 following the special election for District 33. In the Assembly, Republicans have a whopping 21 seat edge after having won 60 of the 99 assembly seats.
Why did Democratic assembly candidates fare so poorly when on the same night Wisconsin voters gave solid wins to President Obama and Tammy Baldwin? Obama won 53% of the vote and Tammy beat Tommy by five, but Democrats won less than 40% of the Assembly. What accounts for these contradictory messages from the voters?
For now I’ll put aside issues of incumbency, fundraising, the ADCC, recruitment, campaigns, and so forth. Instead I focus on what we can glean from raw vote counts. Every assembly district in the state was up for election, so there were no differences between the electorates in the national and state races. We will be in a better position to understand the effects of undervote or ticket splitting patterns after the GAB posts ward-by-ward results, but there is reason to believe that redistricting was the overriding factor, with voter behavior playing a much smaller role, if any.
The graph below shows predictions of the partisan breakdown of the Assembly as a function of the Democratic percentage of the statewide two-party vote. I compute these estimates using assembly district Partisan Vote Index (adPVI) values computed from results of the June 5th recall election for Governor. The adPVI is an extension of Cook’s PVI of US congressional districts to the state level. We can use the adPVI to estimate the percentage of the statewide vote Democrats need to win a given assembly district. In Republican leaning districts we add the adPVI to 50% and in Democratic leaning districts we subtract it from 50%. For example, the adPVI predicts Dems would need 53.4% statewide to win AD 50 (R+3.4) and 44.5% to win AD 55 (D+5.5).
There’s a lot to say about this chart and adPVI. For now, I’ll point out three key conclusions:
- the 39 seats won by Democrats is in line with the adPVI estimates. Obama’s 53.4% and Baldwin’s 52.8% of the two party vote yield estimates of 42 and 40 Democratic seats respectively. This points to redistricting as the dominant factor of the Democratic loss.
- Republicans hold a massive 27 seat structural advantage because of redistricting. This means that in a dead even 50/50 statewide election (point A) the GOP would hold a 63-36 seat advantage in the Assembly. To put this bias in perspective, one analysis of the new maps for US congress, which is widely through to be significantly gerrymandered, gives the GOP an edge of just 13 seats in the 435 seat House or Representatives. So, the assembly district boundaries give WI Republicans more than nine times the structural advantage as afforded congressional Republicans.
- The tipping point for control of the chamber is 55.5% Dem, 44.5% GOP (point B). That means Democrats would need to win by 11 points statewide to have an even chance of winning control of the state Assembly.
There’s much, much more to explore here. I look forward to doing so in the days and weeks ahead.