Let's start where Archbishop Charles Chaput concludes his letter to Colorado Catholics: "the duty of the state and its officials is to serve the common good, which is always rooted in moral truth. A proper understanding of the 'separation of Church and state' does not imply a separation of faith from political life. But of course, it's always important to know what our faith actually teaches."
There seems to be a few people who, shall we say, are ignorant about what the Church teaches about abortion; some people seem invincibly ignorant when it comes to reasonable thinking on life issues and basic human rights as they think it is a matter of personal opinion and that the Church has never really and consistently that human life begins at conception. Listening to Madame Speaker Pelosi on Sunday's "Meet the Press" and in other places Senators Obama and Biden in their political rhetoric, one knows pretty quickly that what they offer is thin gruel. Those who dissent from Catholic teaching ought to be honest and state that they in fact dissent from teaching rather than claim they are "good Catholics." Contrary to Pelosi, the Church is not still making up her mind on matters pertaining to life. The fact is that Speaker Pelosi and Senator Biden, as Catholics, have not embraced the teaching and discipline of the Church. Their position, political and religious, is to publically dissent from the Church's teaching on matters of life and therefore they ought to refrain from the reception of Holy Communion until they repent. Would that the Diocesan Ordinaries of these politicians who claim to be Catholic would do their job and teach and correct error! The salvation of souls is at stake.
According to science and faith (two legitimate ways of knowing), abortion is killing an unborn human being is not a matter which is left to one's mere opinion. In the face of evidence, it is doubtful that anyone can say with conviction that abortion doesn't kill. Clearly the act of abortion revolves less around the choice of a woman to make decisions about "her" body than the fundamental idea which posits the possibility to abort a pregnancy so that a woman to be relieved of a problem or a mistake. There seems to be no reasonable way to argue with people who advocate for abortion until they see/hear the heart beat or feel the kick. The evidence, that is, the biological activity in a woman demonstrates the existence of life at conception. Just wait a month or later in a pregnancy and you will see confirmation that human existence is a fact. AND that fact is defined as a person, not a thing, nor a problem, nor a mistake.
So the Church has been correct for two millennia when she teaches that "Abortion kills an unborn, developing human life. It is always gravely evil, and so are the evasions employed to justify it. Catholics who make excuses for it - whether they're famous or not - fool only themselves and abuse the fidelity of those Catholics who do sincerely seek to follow the Gospel and live their Catholic faith."
Read what Archbishop Chaput teaches his people and apply it to your circumstance. The teaching is correct and objective, faithful and brilliant.