Bähr-Losse is deputy leader of the SPD parliamentary group in the district council of Rhein-Sieg-Kreis. In the Federal election 2013 she ran in Rhein-Sieg-Kreis II, but won no mandate. Since she was second of the SPD party list in North Rhine-Westphalia for the 18th Bundestag, she replaced Peer Steinbrück on 1 October 2016 in the Bundestag. However, at the federal election 2017 she was again unable to win a mandate.