Fairness and power in redistricting

The Colorado Supreme Court has ruled in favor of state Democrats' plan for Colorado's new congressional districts. It's been interesting to listen to the rhetorical arguments on both sides during this drawn-out process. Republicans have been arguing in favor of keeping districts as similar to the previous map as possible, citing the inviolability of county lines (Douglas County is split into two districts in the new map). Of course, hewing close to the current districts aids Republicans, who currently control 4 of the 7 CDs. 

Democrats, for their part, have been arguing in favor of greater competitiveness. Here's what attorney Scott Martinez had to say:

The Supreme Court supported the needs of Colorado families over election-day politics today by creating more modern, competitive districts.... Instead of contributing to the hyper-partisanship in Washington D.C, the court supported Colorado's opportunity to elect moderate candidates who see the needs of our state over the needs of one party or another. In these districts, problem-solvers will win while partisan politicians will struggle, and we are all better off for that.

District competitiveness is an odd goal for a party, as it can mean that more districts swing away from your party in a bad election year. So were the Democrats being foolish in their approach?

In the below graph, I compare the voter registration in the current districts (as measured by the Democratic share of major party active voters) with the figures in the new districts. The green diagonal line charts where the district would be if there were no change; if a district is above the line, its Democratic share of registered voters has just increased.

From this graph, it looks like the Democratic redistricters did the smart thing for their party. They drew some Democratic voters out of their safest districts -- the 1st (held by Diana DeGette) and the 2nd (held by Jared Polis) -- and drew Democratic voters into some Republican-leaning districts -- notably the 3rd (held by Scott Tipton) and the 6th (held by Mike Coffman). The 6th is really seeing the biggest shift. Just a few years ago, this was Tom Tancredo's district, and now it's a tossup.

So, yeah, you could see this as goo-goos moving the state toward greater competitiveness. But you could also see this as a pretty aggressive move by Democrats to break Republican hegemony on one of seven districts.