The Church regards abortion as it regards murder. The Church sees no moral difference.
The Church's position regarding the death penalty is different. The Church has always maintained that the State, in principle, has the right to impose the death penalty for serious crimes like murder. Whether the death penalty should be imposed in particular cases, however, is a matter of prudential judgement.
The current pope has said that since it is now possible in some societies to incarcerate criminals for life without risk to society, there is no need for the death penalty. This is a prudential recommendation, not a repudiation of the death penalty in principle.
Why this furor over a "pro-choice" politician receiving communion and not the same furor over a "pro-death penalty" politician receiving communion?
Because abortion, like murder, is always wrong (except when the mother's life is at risk). It's intrinsically evil. The imposition of the death penalty isn't always wrong. It isn't intrinsically evil.
Kerry after all never committed an abortion and said he is personally against abortion.
Just substitute the word "murder" for "abortion," and the Church's reasoning becomes clear: "Kerry after all never committed a murder and said he is personally against murder, [but he thinks women should have the right to choose murder].
But being a man and not a doctor he will never commit an abortion personally. So what is his sin? Allowing others to be able to commit the sin of abortion? When did allowing someone the free will to commit a sin become a sin?
Failing to work to criminalize murder (abortion), as a legislator, is a grave sin of ommission.