Democrats have no chance at winning back the House in 97 days. (Well, that's not entirely accurate; they have a less than 1 percent chance, according to our Election Lab model.) And, in truth, it might be hard for them — short of a major electoral wave — to retake control for the rest of the decade.

Why? Because the number of competitive seats continues to shrink rapidly, leaving the minority party with very little margin for error. This chart, posted by Brookings and taken from Cook Political Report data, tells the story.

Image courtesy of Cook Political Report

Cook uses something called the Partisan Voting Index (PVI) to compare how every district performs at the presidential level to the country as a whole.  So, for example a district with a D+12 PVI score means the district performed 12 points better for Democrats than the nation as a whole.  Over the last eight election cycles, the number of "swing seats" — those districts with PVI scores between D+5 and R+5 — has dropped from 164 to 90. At the same time, the number of safe Democratic (PVI of D+5 or higher) districts has gone from 123 to 159; the number of safe Republican seats (PVI of R+5 or higher) has gone from 148 to 186.

The main reason for that decline in competitive seats is redistricting processes in 2001 and 2011 that, by and large, shored up incumbents in both parties. It's worth noting in the chart above, however, that the number of swing seats had begun its precipitous decline prior to the 2001 nationwide redraw, suggesting that redistricting is not the only reason for the decline in competition. (I've written that self-sorting — the process of people moving to be around those who think like them — also contributes to it.)

Regardless of the reason(s), what's clear is that the number of targets is on the decline. And there's little evidence that the trend will reverse itself. Writes Cook House editor David Wasserman:

In the 2012 election, 76 percent of Democratic-held seats grew even more Democratic and 60 percent of Republican-held seats grew even more Republican, not taking into account redistricting. As a result, whereas the median Democratic-held seat had a D+7 PVI score in 1998, the median Democratic seat has a D+12 PVI score today. The median Republican-held seat had an R+7 PVI score in 1998; the median Republican-held seat has an R+10 PVI score today.

And, the PVI numbers may actually undersell the true lack of competitiveness.  A look at Cook's list of most competitive races shows only 43 — 23 Democratic-held, 20 Republican-held — seats rated as either toss-ups or leaning to one side or the other. The Rothenberg Political report rates only 36 races as toss ups or leans.

The paucity of targets and the movement in districts across the country toward the respective party poles makes Democrats' task of re-taking the House not only extremely difficult this November but also an uphill climb for, at least, the rest of the decade.