Most immediately, it means that Democrats, while still favored by most analysts to win control of the House, are operating with relatively little room for error because they are trying to gain the 23 seats they need predominantly on one part of the playing field: well-educated suburban seats. Even if they do reach a majority next week, its likely the Democratic hold on the House will be precarious and very slim unless they can also capture a respectable number of the small-town and blue-collar seats now considered toss-ups.
The longer-term implication is that this election now seems highly likely to widen the trench between a Democratic Party that increasingly controls the major metropolitan areas largely skeptical of Trump and a GOP whose dominance is barely dented in the rural and exurban areas where he remains strong.
Already, the CNN analysis shows, about two-thirds of House Republicans represent districts where the education level lags the national average and nearly three-fifths hold seats where the median income is lower as well. By contrast, about 53% of Democrats hold seats where the education level and median income exceed the national average. If Democratic gains next month are concentrated mostly in white-collar seats, the Republican caucus will tilt ever further toward lower-education and modest-income seats while the Democrats will bend further toward the opposite -- expanding the distance between the two sides and making compromise between them even more difficult.