Presidential hopeful and Reason mag pinup Rep. Ron Paul (R-Texas) is a medical doctor who is staunchly anti-abortion. He explains his reasoning over at the blog of the CNN show In The Arena:

In the 1960s when abortion was still illegal, I witnessed, while visiting a surgical suite as an OB/GYN resident, the abortion of a fetus that weighed approximately two pounds.

It was placed in a bucket, crying and struggling to breathe, and the medical personnel pretended not to notice.

Soon the crying stopped. This harrowing event forced me to think more seriously about this important issue....

The fetus has legal rights—inheritance, a right not to be injured or aborted by unwise medical treatment, violence, or accidents. Ignoring these rights is arbitrary and places relative rights on a small, living human being.

The only issue that should be debated is the moral one: whether or not a fetus has any right to life. Scientifically, there’s no debate over whether the fetus is alive and human—if not killed, it matures into an adult human being.

It is that simple. So the time line of when we consider a fetus “human” is arbitrary after conception, in my mind....

If an abortion doctor performs a third-trimester abortion for whatever reason, a handsome fee is paid and it’s perfectly legal in some states.

If a frightened teenager, possibly not even knowing she was pregnant, delivers a baby and she kills it, the police are out en masse to charge her with a homicide. What really is so different between the fetus one minute before birth and a newborn one minute after birth? Biologically and morally, nothing....

Paul states that cases of unprotected sex and rape can be dealt with morning-after pills such as Plan B, which he correctly notes are not "abortion pills" but rather prevent conception from happening in the first place. 

He also argues that he is against Roe v. Wade not because it legalized abortion per se but because it nationalized an issue that should be decided at the state level: " I consider it a state-level responsibility to restrain violence against any human being."

It's a nuanced argument for his point of view and deserves to be read in full, especially if you disagree with him on the matter (as I do). (The post at In The Arena is an excerpt from his book Liberty Defined.)

Further reading: In 2007, Paul introduced the Sanctity of Life Act which asserts that life begins at conception and that federal courts have no jurisdiction over the regulation of abortion. Isn't the first part of that inconsistent with the second? If the federal government has the power to define when life begins (and the "moment of conception" is less clear than it might seem at first blush), then it seems odd that the feds would have no role in its protection. Or slightly differently: If federalism is the issue, shouldn't the bill simply state that the feds have no say in abortion and leave it and the definition of when life begins up to individual states?

Regardless of whether you agree with Paul, I think virtually no other politician lays open his thought process so candidly on the matter.