Think of it this way, any negative right can become a positive right if someone gives it to you. A positive right can’t exist without it.

The 2nd Amendment states that you have the right to keep and bear arms. This means that you can own and utilize a gun for self defense, which is a negative right. It can be made a positive right if the government provides everyone with a a gun for this purpose, but the right to self defense is different from the right to be given the means to accomplish it. Meanwhile the right to vote is something that can’t exist without the government providing it. For $20 I can make a gun with supplies from Home Depot. With $1,000,000 I can’t vote without an existing government system.

Abortion is a function of the right of bodily autonomy and freedom of religion. It’s not the right to have the government “un-pregnant” you on demand, but the right to decide what biological functions you wish to perform. The primary argument against it is based in religious morality, which violates the 1st Amendment’s separation of church and state. The government cannot establish an official religion and impose a specific religious doctrine on you. Since it is something that require you to seek it out and implement it is a negative right.

The real reason abortion is such a delicate political issue is that its true morality is based in religion. If you believe that the soul (a religious concept) begins at or before conception, it is murder which makes it inherently evil. If you believe that the soul becomes a person at viability or birth, it is simply a regulatory restriction like a highway having a speed limit of 60 vs 65 mph. The inability of either side to acknowledge that personal religious beliefs determine whether or not it is literal murder makes a lot of the back and forth shouting an exercise in futility. At the end of the day “Congress make no law respecting an establishment of religion or prohibiting its free exercise.” Saying you can’t do something because someone else’s religion forbids it is a direct violation of that, but ignoring that to some people it is literally murder makes it harder to have honest debates on it. At least having a basic awareness of why the other side is so rabidly opposed to it is very useful in breaking through the emotional arguments that dominate the discussion over the fundamental factors of what is and is not an actual right.