Abortion is just one front in the endless battle against "the principalities, against the powers, against the world rulers of this present darkness, against the spiritual hosts of wickedness in the heavenly places." (Ephesians 6:12)
Discerning the Body: The Bishops, The Politicians, and The Eucharist
The issue here is not that the politicians in question are politicians per se, it is that that as prominent people they are publicly using their influence to promote things that are gravely sinful. When those responsible for teaching, governing, and sanctifying fail to distinguish the true dimensions of the problem, and fail to govern by allowing those who persist in openly promoting sin to receive communion they are teaching, by their actions, that the Body and Blood of Our Lord is simply not that important.