What's wrong with this logic?

You should vote for a politician that is for abortion even though it doesn't effect you but it could effect your nieces. Therefore thats why you should vote for a politician that supports abortion.

I don't think this argument is inherently illogical, but it does have some flaws.

Politicians are going to campaign on a wide variety of social and economic issues. The person making this argument seems to be making an assumption that their decision whether or not to vote for this particular politician could come down to their stance on abortion. This is true for some people, but probably not most.

For the second part: It's clear that the speaker is trying to convince the other person that their vote should reflect a more collective interest, rather than pure self interest. Choosing the person's nieces as the people who may need an abortion does add a certain emotional stake to it that could break a person out of a mindset of pure self interest. But, at the same time, it's also likely that his nieces won't need abortions, in which case it's all a hypothetical that won't pan out. I think the right way to resolve this would be to broaden it out, and tie it in to the fact that abortion laws do affect a large segment of the population of women. Say something more like "It will affect women like your nieces."

Among others, it is the Fallacy of Tunnel Vision (Big Picture).The big picture is the totality of a situation. In analyzing a problem, the analyzer needs to know how each part fits into the larger whole. A well-intentioned person trying to do his best work and hyper-focused on one aspect (Tunnel Vision), yet utterly oblivious that his job is part of a larger project. He needs to see the Big Picture.

For example, suppose candidate A advocates abortion and the self-destruction of the country. Candidate B disagrees with abortion, but advocates survival of the country. If A wins, there is no country and abortion rights are meaningless. If B wins, the country survives and there is an ability to change law. 

The logic presented in the argument has several issues, including vague reasoning, assumption of universality, and a potential appeal to consequence:

1. **Assumption of Universality (False Dilemma):** The argument appears to assume that supporting or not supporting abortion is the only pertinent issue when voting for a politician. This disregards a multitude of other factors that might also be important, such as economic policies, healthcare, education, and foreign policy. Suggesting that one must vote based on this single issue alone presents a false dilemma, limiting the complexity of political decision-making to an overly simplistic binary choice.

2. **Appeal to Consequences (Emotional Appeal):** The argument uses the potential impact on "your nieces" as a reason to support a politician who favors abortion. This is an appeal to consequence, which can skew logical reasoning by focusing on potential outcomes rather than the merits of the policy itself. Arguments should be based on well-rounded reasoning rather than emotional appeals about potential personal impacts.

3. **Vagueness and Lack of Specificity:** The argument is vague in its reasons for supporting a politician that favors abortion. It does not provide concrete evidence or logical propositions about why this issue is critical, nor does it give a detailed analysis of how the policy will affect the nieces or society as a whole.

4. **Irrelevant Conclusion (Non Sequitur):** While the potential effect on nieces is a consideration, the argument jumps from this hypothetical scenario directly to a conclusion that voting for a pro-abortion politician is necessary. This leap in logic does not follow directly from the premise, making it a non sequitur. There is a lack of a coherent connection between the concern for nieces and the overall argument for voting based on this issue alone.

To construct a stronger argument, one could provide a balanced, well-rounded consideration of various political issues, supported by evidence and logical reasoning, while being mindful of emotional appeals and simplistic solutions.