Voting for a pro-abortion politician when a plausible pro-life alternative exits constitutes material cooperation with intrinsic evil, and those Catholics who do so place themselves outside of the full communion of Christ’s Church and under the judgment of divine law. Persons in this condition should not receive Holy Communion until and unless they are reconciled to God in the Sacrament of Penance, lest they eat and drink their own condemnation.
But the assumption behind the statement is faulty. There was no "plausible pro-life alternative." Yes, there was an anti-abortion candidate, but just being anti-abortion doesn't make you pro-life. Being pro-life means holding up the life as the original value against everything that threatens it in the culture of death: abortion, capital punishment, pre-emptive war, structures of poverty, and disregard for the health of the creation. My implication, of course, is that neither of the two major candidates for president in this recent election lived up to these values enough to earn the label "pro-life." In fact, the only candidate I know of that seems to get it is Joe Schriner, a good Catholic by the way. I learned of him through a kind reader of this blog, and I have actually corresponded with him since. Give him your support in whatever he decides to do next with his campaigning.
We must pray for our president-elect's party that it might come to value the life of the unborn. We must all do our part to repent of all of our culture's sins against the sanctity of life, abortion especially. But we can't pretend that what secular politics calls "pro-life" is what is really implied by the term at its deepest Christian level, and we certainly can't let these compartmentalizations and oversimplifications into the Body of Christ.