It sounds like you're saying, "I hypothesize that exposure to radio influences women's electoral participation. I'm going to measure exposure to radio in two ways: 1) frequency of listening to the radio, and 2) political knowledge. Therefore, if frequency of listening to the radio and/or political knowledge influences women's electoral participation, then I will have evidence supporting my hypothesis." (I'm leaving out the mediating variable for the sake of simplicity.)

If I'm understanding you correctly, then support for your two sub-hypotheses provides support for main hypothesis.