It is not sufficient for Catholic politicians to claim that they are ‘personally opposed’ to abortion. If any Catholic politician favors legalized abortion, despite a claim of personal opposition, such a politician commits a mortal sin by promoting abortion and by voting in favor of abortion.
The same is true for any Catholic who casts any vote with the intention of legalizing abortion, or of protecting laws allowing abortion, or of widening access to abortion. Such a voter commits a mortal sin and incurs a sentence of automatic excommunication for two reasons. First, they are committing the sin of heresy by believing that abortion should be legal and available. Second, they are committing the grievous sin of providing women with substantial or essential assistance in obtaining abortions, by attempting to legalize or broaden access to abortion.