Any Catholic able to support a politician who supports and actively calls for abortion is either unaware of the teaching of their Church or consciously acting against it.
Abortion is defined by the magisterium of the Catholic Church—since its very beginning—as a moral evil resulting in excommunication for those involved in either direct abortion or formal cooperation in abortion.
Here are the relevant sections of the Catechism regarding abortion:
“2271 Since the first century the Church has affirmed the moral evil of every procured abortion.
"This teaching has not changed and remains unchangeable.
"Direct abortion, that is to say, abortion willed either as an end or a means, is gravely contrary to the moral law:
“You shall not kill the embryo by abortion and shall not cause the newborn to perish.
"God, the Lord of life, has entrusted to men the noble mission of safeguarding life, and men must carry it out in a manner worthy of themselves.
“Life must be protected with the utmost care from the moment of conception: abortion and infanticide are abominable crimes.
“2272 Formal cooperation in an abortion constitutes a grave offense.
“The Church attaches the canonical penalty of excommunication to this crime against human life.
"A person who procures a completed abortion incurs excommunication latae sententiae," "by the very commission of the offense," and subject to the conditions provided by Canon Law.
"The Church does not thereby intend to restrict the scope of mercy.
"Rather, she makes clear the gravity of the crime committed, the irreparable harm done to the innocent who is put to death, as well as to the parents and the whole of society."