Thursday, the Senate Internal Affairs Committee released its redistricting plan for the 24 state Senate districts. To help understand the electoral implications of the plan, I’ve compared the Partisan Voting Index (PVI) for the proposed districts to that of the the current districts. (See the New Hampshire Partisan Voting Index (PVI) for a discussion of the Cook PVI and methodology.)
Observers from Rep. Steve Vaillancourt to Paul Twomey have said this plan could have been a lot worse for Democrats. Nevertheless, the proposal clearly improves Republican electoral chances by concentrating Democratic votes in current Democratic strongholds. Four of the five districts with seats held by Democrats today will become even more Democratic under this plan. The fifth Democratic seat, held by Sen. Lou D’Allesandro, is unchanged — despite rumors that it would be targeted for a Republican takeover.
Meanwhile, nine of the 16 Republican incumbents seeking reelection will benefit from a more Republican-leaning electorate; five will run for reelection in districts with exactly the same make-up as before. The big winners are Sen. Fenton Groen, whose district will be four points more Republican, Sens. Russell Prescott and Bob Odell (five points more Republican) and Sen. Nancy Stiles (seven points more Republican).
The proposed plan will have a public hearing Wednesday at 1:00 PM in LOB 205/207. The Senate will likely vote to adopt the plan on January 25. A district-by-district analysis follows below the fold.
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Wednesday, the House Special Committee on Redistricting released the House leadership’s redistricting plan. The plan, which creates new voting districts for the state’s 400 House members, reflects population shifts measured by the 2010 census.
This plan varies dramaticially from the current plan due, in large part, to a 2006 constitutional amendment that requires every town and city wards with the minimum population to get its own representative. This proposed plan expands the number of districts from the current 103 to 200.
To help understand the electoral implications, I have updated my original analysis of the partisan makeup of House districts based on this plan. (See the New Hampshire Partisan Voting Index (PVI) for a discussion of the Cook PVI and methodology.) This chart provides the Partisan Voting Index (PVI) for each new district.
Using methodology similar to that I used to project the 2010 state House elections (Part 1, Part 2), I projected electoral results using the current House districts and compared them to projected results using the districts in the proposed plan. The projections indicate only a 1-2 seat gain for Republicans in state-wide results in the new plan, well within the model’s margin of error. For example, the model indicates a 202-198 Democratic majority under the current plan would become a 200-200 tie under the proposed plan.
In the next few days, I’ll take a closer county-by-county look at the new plan and the electoral projections.
Matt Breuer, an undergraduate political science student at Yale, has undertaken an ambitious project to measure and document the partisanship of every U.S. state legislative district. Breuer’s Legislative District Index is based on a weighted average of the results in six presidential, gubernatorial and legislative races and is relative to the average result for the state.
Today, Breuer released the LDI for New Hampshire. I did a quick comparison between the Breuer’s LDI and my PVI calculations for the state’s 103 House districts. The two indexes are quite consistent when comparing the relative partisan ranking for each district. For example, the two indexes share 8 of the 10 most Republican districts and 8 of the 10 most Democratic districts.
Compared to PVI, the LDI margin is more exaggerated in the most partisan districts. For example, Grafton-9, the most Democratic district in most indexes, has a PVI of D+28 and an LDI of D+43. Hillsborough-18, the most Republican district in both indexes, has a PVI of R+12 and an LDI of R+25.
The New Hampshire LDI data is available for downloading. Thank you to Matt Breuer for providing this valuable analysis.
Update: Breuer notes that LDI measures the vote margin between candidates, while PVI measures one-party vote share. For an apples-to-apples comparison, you should divide LDI by two (or double PVI).
Earlier this week, the U.S. Census Bureau released the results of the 2010 Census for New Hampshire.The census data will be used by the legislature to realign the state’s congressional and state legislative districts.
The chart below shows the population data for each of New Hampshire’s towns, combined with the Partisan Voter Index (PVI) data from my earlier study. Here are a few interesting tidbits:
- Grant Bosse calculates Carroll (R+1), Grafton (D+9), and Merrimack (D+4) counties will each gain an extra state Representative. Coos (D+4), Cheshire (D+11), and Hillsborough (R+1) will each lose one.
- 20 New Hampshire towns and cities gained more than 1000 residents over the decade, led by Dover with a population gain of 3103. The 20 are evenly split between Democratic and Republican partisan voters. Ten have a R+ PVI, ten have a D+ PVI.
- Two of the top five are Republican strongholds: Bedford (+2929, R+12) and Windham (+2883, R+11). Two are strongly Democratic: Dover (+3103, D+11) and Concord (+2008, D+12).
- 54.7% of the state’s residents live in Democratic-voting (D+ PVI) towns, down from 55.5% in 2000 (based on current PVI).
For more census data analysis, check out the the New Hampshire Center for Public Policy’s studies on New Hampshire’s shifting population: Patterns of Growth and Census 2010.
Nate Silver is at it again.
Silver analyzed open-seat Congressional races to determine if there are systematic differences in voter behavior between voting for President and for Congress. This was to help explain why the Congressional vote in certain districts is more Democratic or Republican than Cook’s Partisan Voting Index (PVI) alone would suggest.
Silver determined the one predictive factor—in addition to partisan Presidential voting—is socioeconomic status. Relative to the Presidential vote, Democrats are somewhat more likely to win Congressional races in poorer districts, and somewhat more likely to lose them in wealthier ones.
After running a copious number of logistic regression models on a copious number of variables, the only other thing that seems unambiguously to matter is socioeconomic status, which I measure by the percentage of households with incomes below $25,000. This is pretty unambiguous, in fact, as the variable has predictive power at the 99.9%+ plus certainty level.
Thus, Partisan Propensity Index, or PPI, is defined as the percentage chance that the Democrat would have won and open-seat race for Congress in a particular district given the conditions present, on average, between 2002 and 2008…It contains only two variables: the Presidential vote share in the district and the percentage of households there with incomes below $25,000.
PPI calculations for New Hampshire’s two Congressional districts are below the fold.
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The next (and last?) chapter in my look at the partisan makeup of New Hampshire voters is a study of the 103 districts for the state House of Representatives. This is a follow up to earlier looks at the voting wards and the state Senate districts.
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I have consolidated the voter ward data from my initial New Hampshire Partisan Voting Index study to take a look at the partisan makeup of New Hampshire’s 24 state Senate districts. (For an introduction to the Cook PVI and my methodology, refer to the original diary.)
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When I rolled out the New Hampshire voting ward PVI maps, one of the commenters referred to their predictive value. It’s an interesting comment. In my mind, the index has clear value as a means of measuring and comparing voting patterns across districts. But can it also be used to help predict election results?
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The Cook Partisan Voting Index (PVI) compares how a congressional district votes relative to the nation as a whole. The index objectively measures each congressional district as a means to allow comparisons between districts that are relevant in both mid-term and presidential election years.
The index is derived by averaging a district’s voting results from the previous two presidential elections and comparing them to national results. The result indicates the number of percentage points by which the party’s vote exceeded the national average.
For example, a D+2 PVI means the district performed two points more Democratic than the nation did as a whole in the 2004 and 2008 presidential elections. The Democratic candidates would have received roughly 53.3% of the two-party vote compared to the national two-party average of 51.3%.
Using this same methodology, I have calculated the PVI for each New Hampshire voting ward and created a map of the results. 158 of the state’s 299 voting wards with at least 25 votes in the 2008 presidential election lean Democratic. They are led by Hanover as the most Democratic ward in New Hampshire with a D+29 PVI. 118 wards lean Republican. The most Republican voting ward in the state (with at least 200 votes) is New Ipswich in Hillsborough county with a R+16 PVI.
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