In general, applicants for a master's in teaching history do not need to possess a B.A. in history, so you'll be able to apply with a degree in political science. For example, the University of Illinois at Chicago specifically states that you don't have to be a history major to apply for their M.A. in Teaching History program.
In applying to a history teaching program, you may want to highlight the connections between political science and history and list any history courses you have taken. You'll need to demonstrate your passion for history, as a nonhistory major, to increase your chances of admission.
As a political science major, you should make sure your program includes coursework or electives in history so you are sufficiently qualified to teach it. For example, the University of Illinois at Chicago's Master in Teaching History program requires 32 credit hours in history, with at least 16 of those hours at the graduate level.