How many constituents does your representative represent?

This story is excerpted from the MT Lowdown, a weekly newsletter digest containing original reporting and analysis published every Friday.

As legislators meet this winter to craft new laws and negotiate the next state budget, a quirk of Montana’s Constitution means there’s a notable misalignment in the state’s political math: Every representative has one vote on the floor of the Montana House of Representatives, but some represent thousands of constituents more than do their neighbors a few seats over.

The state’s current legislative districts, adopted in 2013, evenly divide the state’s population as it was counted by the 2010 census. Since that count, though, certain parts of Montana have added residents at breakneck speed while others have held steady or even lost population.

The state Constitution specifies that legislative districts are rebalanced following every decade’s national census count, but it also lays out a timeline that creates the demographic equivalent of a lame duck congressional session by giving lawmakers elected under the old map a chance to comment on the new one drawn by the state’s independent Districting and Apportionment Commission.

As that process plays out in this year’s Legislature, data compiled by the state Census and Economic Information Center shows just how far out of whack the state’s political boundaries have gotten.

In several cases, 2010 districts saw their populations swell by 50% or more. That means, for example, that House District 65’s Kelly Kortum, a Democrat who now has about 17,800 constituents in northwest Bozeman, represents nearly twice as many people as does, for example, House District 1’s Steve Gunderson, a Republican with about 9,500 people in his Libby-area district.

Notably, however, overpopulated districts have elected both Republican and Democratic representatives this year, meaning the aging political map’s misalignment doesn’t confer either party an obvious political advantage. South of Kortum’s district, for example, Republican Rep. Jane Gillette represents an overstuffed House District 64 of about 14,500 people — and Republican lawmakers this year represent about 10,800 constituents on average, compared to 10,900 for Democrats.