Sometimes it is useful to look at an actual dictionary definition of the word you are working with. Merriam-Webster defines politics as: The activities associated with influencing the actions and policies of a government. That is one way to look at it.
Another possible definition is "the exercise of power to influence the actions of a group or a government." This definition is similar, but it specifically touches on the idea of power as the central component in getting things done. Let's face it, nothing happens without the power to make it happen. That power could come from several possible sources. It could be the power of influence, authority, coercion, money, or even morality.
You are looking at abortion in this context. Abortion is political because of the conflict concerning its legality. Laws must be passed that either make it legal or illegal. The process of passing laws in steeped in politics. We usually think of the abortion issue as revolving around morality--is it morally right or wrong? Morality has political power because people will support causes that they feel are morally correct. Some elected officials are able to exercise political power based on morality if they represent districts that are clearly pro- or anti-abortion.
However, morality is not the only aspect of power involved in the abortion issue. If a group is trying to get an anti- or pro-abortion bill passed, they will have to use other kinds of political power to get it done--they will have to influence other lawmakers to vote with them. This may involve political favors, such as promising to help someone's political career in some way, or promising to support an issue that they are interested in.