Democrat Sean Casten unseated Republican incumbent Peter Roskam in a House race in the 6th Congressional District in Illinois. Does this signal the end of Republican dominance in this suburban district? Some points to consider:

1. This has been a Republican district since the early 1970s. Before that, the District was represented by a Democrat since the late 1920s and dominated by Republicans between the Civil War and 1911. Long-time representative Henry Hyde passing the seat to Peter Roskam may be the recent history but the district has more variation over the years.
2. The demographics of these suburban areas has changed quite a bit. Like many American suburbs, the Chicago suburbs have become increasingly non-white and more diverse in terms of social class. The area covered by the district today is not the same white, middle-class swath that it may have once appeared to be.
3. Redistricting and changing boundaries has happened with the 6th in the past and could happen again in the future. Read more about Illinois redistricting efforts in the 1970s and early 2000s. Some background on this particular district:

Roskam replaced conservative icon U.S. Rep. Henry Hyde in Congress, but much of his old territory in eastern DuPage County is now represented by U.S. Reps. Mike Quigley of Chicago and Raja Krishnamoorthi of Schaumburg, both Democrats.

4. The patterns of voting in the Chicago area suburbs mirror larger trends about suburban voters. The 6th district as well as several other House districts are comprised of the middle ground between Democratic voters in the big city and close suburbs and Republican voters in more rural areas and outer suburbs. These are the battleground areas and this will likely continue in future election cycles.

All this said, there are no guarantees in this district. Multiple factors could sway voters in this district in the near and far future including changes in what the national parties stand for (and what presidential candidates are leading the way), increasing diversity in the suburbs, possible redistricting, and particular concerns and issues that may resonate voters in the middle suburbs. As the suburbs continue to be important areas for both parties to try to pick up seats, expect this district to continue to be contested for at least a few elections to come.