The Communist Party website is stating which races they are trying to influence.
https://www.cpusa.org/article/election-2018-a-guide-to-united-action/Congress:
In the House Democrats need to flip 24 Republican seats in addition to holding on to the 194 seats they have to be in the majority. We are involved in 38 Republican seats that can be flipped: AZ, CA – 7, CO, FL-2, IL-2, IA-2, MI, MN-2, NJ-3, NY-3, OH-2, PA-5, TX-3, VA-4, WA-2, WI.
In the Senate 24 Democrats and 9 Republicans are up for re-election, a total of 35 seats. Democrats need to win 28 of the 35 seats to gain a majority.
We are involved in two states where a Republican seat can be flipped: AZ (Flake open), TX (Cruz), and five states where a Democratic seat needs protection against being lost: FL (Nelson), IN (Donnelly), MO (McCaskill), NJ (Menendez)