Johanson, the former executive director of the Democratic Congressional Campaign Committee and chief of staff to House Minority Whip Steny Hoyer (D-Md.), managed Sen. Tammy Baldwin's (D-Wis.) historic campaign in 2012.
“Karin has proven that she can win tough races. She has taken on and beaten a full arsenal of failed leadership, despite millions in negative ads,” Davis Communications Director Bo Delp said in a statement. “Karin will be an excellent and outstanding addition to this historic and exciting campaign.”
Davis announced her gubernatorial bid earlier in October.
"As long as we can make this great state even greater, we will keep going," she said during her announcement in Haltom City, Texas. "Because with the right kind of leadership, the great state of Texas will keep its sacred promise that where you start has nothing to do with how far you can go."