I saw this too, and was going to post it. This seat is gone.
Bold prediction: Duckworth wins this year, loses in 6 years to a Republican, who, in turn, loses to a Democrat in 2028.
While I'm aware that this seat has switched parties every cycle in the past since Braun lost to Fitzgerald, Duckworth isn't going to lose to a Republican in Illinois, even in a midterm.
The fact that she is WAY underperforming Clinton even as Trump is in the middle of what could be an implosion shows she is not as strong of a candidate as people think. If 2022 is at least a neutral year, Dold can win. Rodney Davis, Peter Roskam, and Adam Kinzinger are possibilities, but they're all pro-life and pro-gun, which will really hurt them.
Do you think a Democrat will be president in 2022?
Overall, no. But if that is the case, Davis, Roskam, or Kinzinger can win. Dold can still win in a 2022 midterm with a Republican president, unless it's a 2006/2008 level wave. Do not underestimate Dold, or overestimate Duckworth. If Dold wins this year, I think he wins again in 2018, and then becomes entrenched.
No Republican is going to be entrenched in a D+8 district in this polarized era.