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AP: No clear partisan slant in New Mexico House districts

March 21, 2019
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New Mexico Sen. John Sapien, D-Bernalillo, left, meets with Democratic House Speaker Brian Egolf on the House floor on Friday, March 15, 2019 in Santa Fe, N.M. The Democratic-controlled New Mexico Legislature ended Saturday, March 16, 2019, after passing bills to increase education spending and create an independent ethics commission. (AP Photo/Russell Contreras)

SANTA FE, N.M. (AP) — Democrats in the New Mexico House posted one of the largest gains nationally in last year’s elections — picking up even more seats than would have been expected based on their share of the vote, according to an Associated Press analysis.

The 21 percent increase in Democrats’ seats helped them build a supermajority in the New Mexico House during what was generally considered a good year nationally for Democrats.

The Associated Press examined all U.S. House and 4,900 state House and Assembly seats up for election last year using a statistical method of calculating partisan advantage that is designed to flag cases of potential partisan gerrymandering. Although New Mexico Democrats enjoyed an advantage in 2018 under a court-brokered plan, the same districts had produced a slight Republican edge in the 2016 elections, according to the AP’s “efficiency gap” analysis.

The analysis found that Democrats won about three more seats than would be expected in 2018 based on the party’s average share of the vote in state House districts. The same analysis in 2016 found that Republicans won one or two more seats more than expected.

Those back-and-forth election gains, along with AP calculations of the efficiency gap swap, suggest that New Mexico’s districts ultimately do not have a significant partisan slant, said Brian Sanderoff, an Albuquerque-based pollster and president of Research & Polling Inc.

“There wasn’t a dramatic efficiency gap that skewed to the same party in both election cycles,” said Sanderoff, who served as a rules expert in New Mexico’s 2011-2012 redistricting litigation.

The efficiency gap model was developed by Eric McGhee, a researcher at the nonpartisan Public Policy Institute of California. He said that if a modest efficiency gap advantage disappears for one party and crosses over to the other during a series of elections, then there’s probably no reason to suspect significant political gerrymandering of those districts.

The current New Mexico state House districts were drawn in 2012 by a state district court after former Republican Gov. Susana Martinez vetoed a plan from a Democratic-led Legislature.

The court worked off a redistricting plan submitted by the Martinez administration and made several modifications with the assistance of an expert. The court’s goal was to minimize partisan leanings and keep intact communities with similar cultural, economic or geographic concerns.

In 2014, which was a good year nationally for Republicans, the GOP won a narrow majority in the New Mexico House for the first time in six decades. But it didn’t last long. In 2016, Democrats won a 38-32 majority over Republicans. In last year’s elections, that ballooned to a 46-24 Democratic majority.

Democratic Gov. Michelle Lujan Grisham’s first term runs through the scheduled 2021 redistricting, and Democrats have incumbent majorities entering the 2020 House and Senate elections. That could create an opportunity for gerrymandering by the party in the next round of redistricting following the 2020 Census.

“When the executive and legislative branches are of the same party, they are more likely to be tempted to pass a more partisan plan,” Sanderoff said. “There’s still one more election cycle, but it’s starting to look like there could be a majority of Democrats in the House and Senate.”

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