If you headed the DCCC in 2018.....

[Since I'm the mad scientist proclaimed by myself]

AZ-02 (There was no excuse for Democrats to not even compete here in 2016; the fact Clinton won this district I hope makes them take a second look - the seat was won by literally hundreds of votes in 2012 and 2014.)

The candidate was very bad.

[Since I'm the mad scientist proclaimed by myself]

Iowa can be competitive with the right candidates. Matt McCoy is pretty disliked among many of the state's Democrats, so I wouldn't get him to run. I'd agree with Liz Mathis in IA-01 (though I personally am hoping Anesa Kajtazović tries again - she ran in 2014 and lost to more well-known candidates, but I really liked her; plus she's young).

Where Democrats failed with Monica Vernon was the fact that they invested very little money in the seat, as they assumed it would be an automatic pickup. It wasn't until closer to the election that they realized that maybe Obama's voters wouldn't turn out for her. And, unfortunately, they didn't. I've noticed Iowans tend to be very stubborn when it comes to their candidates; among my friends, at least, many Sanders supporters adamantly refused to back Clinton and went for Johnson instead. They probably didn't even vote in the House races. Iowa's not a lost cause for Democrats; they just need to do better recruiting (IA-03 especially; Staci Appel was pretty disliked when she was still in office, even among Democrats - I've met her, and while she was a nice person, there was something about her I didn't like. And national Dems never did seem all that excited about Jim Mowrer, for some reason).

A few other seats I'd target besides IA-03 and IA-03:

AZ-02 (There was no excuse for Democrats to not even compete here in 2016; the fact Clinton won this district I hope makes them take a second look - the seat was won by literally hundreds of votes in 2012 and 2014.)

CA-49 (Applegate came very close to knocking off Issa; I'd like to see him try again in a Trump midterm)

CO-06 (I don't know what it is with Coffman, but every single one of his candidates looks competitive on paper but can't knock him off. Still, with a Trump midterm, I hope they try again)

FL-26 (I hope Joe Garcia finally takes the hint that voters don't want him back - I knew as soon as he won the primary, this seat was lost. Maybe get Annette Taddeo to come back, or find another candidate)

FL-27 (Clinton won the district, but IRL is probably too entrenched to defeat. Wouldn't hurt to get somebody to run though)

GA-06 (The fact that Clinton narrowly won this shocked me; Democrats NEED someone here)

KS-03 (Another Clinton district with an incumbent who could be vulnerable in a Trump midterm.)

KY-06 (Jim Gray, who lives in this seat, actually won it during his senate race. I hear he's seriously considering challenging Barr. It frustrates me that Democrats have ignored this seat ever since Chandler narrowly lost it)

ME-02 (ANYBODY but Emily Cain. When she announced her rematch, I actually felt uneasy. She was the one rematch I was not looking forward to)

MN-02 (I'm still shocked that Lewis actually won this)

MT-AL (Juneau should give it another shot when it opens up with Zinke's confirmation)

NE-02 (Ashford only narrowly lost, though Bacon seems like he'd be popular. It'd be worth recruiting somebody for)

NJ-07 (Lance isn't popular in his own party, and Clinton won this district)

NY-01 (I'd like to see what Calone could pull off)

NY-19 (I don't know that I'd go with Teachout again, but this was a pretty close one)

SD-AL (Noem's retiring, and Democrats held this seat until 2010, so why not go for it?)

TX-23 (Gallego's loss was pretty shocking, but Democrats need to compete here.)

VA-02 (Absolutely no excuse for Dems' recruitment failure here in 2016; they need to try again)

VA-10 (I really hope Dems don't give up on this district)

They didn't compete in Arizona 2 because McSally raised a startling sum of money. She's a rising star; the RCCC wasn't about to lose her. It was more financially viable to be competitive elsewhere, so I do think there was reason.
And...
SD trended massively R. I think California is more viable for them to target than South Dakota.

McSally raised a lot because her district was competitive,  the same can be said of Barb Comstock, Erik Paulsen, or Jeff Denham.   The donors know where to send the money.    I don't think McSally is a rising star,  she's quite socially conservative and takes some really hardline approaches to birth control and maternity leave.   She definitely has a lot of weak points to exploit.

McSally had a really incompetent opponent in 2016 who had no idea how to fund-raise and almost didn't have a campaign(the only things I heard about him were attack ads against him).