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Politics

Republicans' Gerrymandering Could End Up Helping Democrats

The party redrew lines to create many slightly Republican districts. Those now look vulnerable.

The Tea Party wave of 2010 cost the Democrats the House, and then Republicans gerrymandered congressional districts to remain in power. But drawing districts with the intention of helping your party is an act of statistical modeling, and all models have assumptions, biases and flaws. A midterm election with an unpopular Republican president will reveal some of the flaws in the Republican Party's gerrymandering. The redrawn lines may even benefit Democrats.

The House gerrymander that Democrats complain about is mostly a phenomenon in five states -- Michigan, North Carolina, Ohio, Pennsylvania and Virginia. President Barack Obama carried all five states in 2008, yet after the 2010 Census, Republicans in those states drew district maps that were very favorable to their party. Those five states have a combined 73 seats in the House -- currently 52 Republicans and 21 Democrats. Those 73 seats are all held by the party favored to hold those districts, according to the Cook Partisan Voting Index.

The Cook PVI measures how much a district leans Republican or Democrat relative to the national average, as measured by an average of the most recent two presidential elections. If Democrats won a national election by two percentage points, as they did in 2016, a Cook PVI score of D+2 would mean that a district is 2 percent more Democratic than the national average, or a nominal Democratic margin of four points.

Drawing districts in such a way that your party benefits is a delicate operation. If you're a Republican and you have 10 districts to work with, you might be tempted to tilt as many of them as possible toward your party -- say, by creating eight R+1 or R+2 districts. But those eight seats would be vulnerable. If instead you choose to make four of the 10 districts solidly Republican -- for instance, R+10 districts -- you give yourself some safe seats but put extra territory in play for Democrats to take advantage of. With partisanship as entrenched as it currently is, the sweet spot has been around R+4 or R+5, a margin presumed to be safe in normal elections.

The five heavily gerrymandered states mentioned above show this in action. Of the 21 Democratic seats, 19 are D+8 or higher, with the other two being a D+4 and a D+6. Even in a historic Republican landslide, Democrats might only have those two seats at risk. Yet the Republican list looks much different. Fourteen seats are R+4 or less, with an additional 10 seats being R+5 or R+6. Trying to distribute their supporters across as many districts as possible, Republicans created many weakly Republican districts rather than a few strongly Republican districts. The party gambled on politics as usual. And then Donald Trump became president. If you're a Democrat, this is where your ears perk up.

Polarization is high in the recent political climate, but so is congressional turnover. Democrats picked up 30 seats in the 2006 midterms and another 21 in 2008. Then Republicans picked up 63 seats in 2010, and after giving a few seats back in 2012, expanded their margin in 2014.

Midterm elections tend to have lower turnout than presidential years. We don't yet know what the demographic makeup will be of a Trump midterm election. For all we know, Republican-leaning working-class white men will stay home, while Democratic-leaning women and college-educated voters are mobilized.

And at this point in the presidency, Trump is currently the least popular president ever. Much can change over the next 21 months. But if things don't improve for him, there's no reason to think he and his party would be any different than every other unpopular president heading into a midterm election.

Here's where the "Republican gerrymander" could help Democrats. In a big enough anti-Trump wave, the R+4 districts intended to favor Republicans could tip toward Democrats.

After the Democratic waves of 2006 and 2008, the Republican wave of 2010, and Trump's unexpected election, pundits must question their assumptions -- and those of the Republican Party. Its gerrymander could cost it the House.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

    To contact the author of this story:
    Conor Sen at csen9@bloomberg.net

    To contact the editor responsible for this story:
    Philip Gray at philipgray@bloomberg.net

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