Contrast is surely the leaven of politics. And nothing highlights worldview differences better than candidates’ and legislators’ positions on sanctity of life issues.

There’s almost no issue that candidates, political parties and legislators try to avoid more. They hope that it will go away, even though voters who care about life issues consistently provide a winning margin in tight races.

The fact is, the issue will continue to be hotly debated until the abortion-on-demand regime of Roe v. Wade begins to unravel and our nation’s citizens are given the chance to enact each state-by-state consensus on what abortion laws should be.

I understand abortion rights advocates’ panicked protest at that prospect. I used to share it.

Now is the time to look very closely at candidates. We are at a turning point in history when it comes to abortion and euthanasia. The voters who decide the next president and Senate will also decide the makeup of the Supreme Court and federal judiciary for generations.

An especially telling difference exists between Sens. Barack Obama, D-Ill., and John McCain, R-Ariz.

How each perceives and talks about unplanned children is extremely illuminating. McCain is living the joy of his real-life response to a “surprise child.” Obama, missing the mystery and blessing, sees only a burden.

You may remember from a few weeks ago, Obama’s answer to a question at a town hall meeting regarding HIV and STDs: He said, “Look, I got two daughters — 9 years old and 6 years old. I am going to teach them first about values and morals, but if they make a mistake, I don’t want them punished with a baby”

He sees such a surprise baby as punishment for wrongdoing rather than the natural result of a bad decision to engage in sex.

In the Illinois Legislature in 2002, Obama voted against a bill to require life-sustaining measures for babies who survive late-term abortions and are born alive “accidentally.” Then, in 2003, he killed this measure in the Illinois Senate Health committee he chaired.

His perspective on these “surprise” children: “What we are doing here is to create one more burden on a woman, and I can’t support that,” said Obama in 2003.

That’s a living human being he would allow to die because he judges it to be an expendable annoyance. For him again, the unexpected born baby is a punishment and burden — an unnecessary affront to the woman’s decision to abort.

I understand Obama’s position because I once held it.

I considered myself “pro-choice” because I did not believe the surprise child had separate rights from my own. In that case, a surprise baby is an invading visitor, an unasked-for imposition.

But technology advanced and my opinion, along with that of so many others, changed. Sonography, fetology and compassionate friends all convinced me of the existence of two human beings with rights and needs.

Obama has resisted the pro-life trend in this nation that is documented in poll after poll. Perhaps thinking he will attract women voters, he clings to the proposition of baby as burden — that of the powerful over the weak. This will not help him.

That’s not only because women themselves — especially younger ones — are moving away from the abortion position. It is also because the position of generosity and love is the stronger, more attractive position.

Who can resist Mother Teresa? She helped the world understand the stark contrast between the view of children as burdens or as gifts. She could see clearly the divisiveness inherent in the abortion position.

Quoted in The Wall Street Journal, she said, “America needs no words from me to see how your decision in Roe v. Wade has deformed a great nation. The so-called right to abortion has pitted mothers against their children and women against men. It has sown violence and discord at the heart of the most intimate human relationships. It has aggravated the derogation of the father’s role in an increasingly fatherless society.

“It has portrayed the greatest of gifts — a child — as a competitor, an intrusion and an inconvenience. It has nominally accorded mothers unfettered dominion over the independent lives of their physically dependent sons and daughters.

“And, in granting this unconscionable power, it has exposed many women to unjust and selfish demands from their husbands or other sexual partners. Human rights are not a privilege conferred by government. They are every human being’s entitlement by virtue of his humanity. The right to life does not depend, and must not be declared to be contingent, on the pleasure of anyone else, not even a parent or a sovereign.”

Contrast the perspective of baby-as-expendable-burden and punishment with the rarely repeated story of John and Cindy McCain’s “surprise” child.

Sen. McCain told me this story of their family, and, on another occasion, Cindy McCain related it. Both times I heard the story — each from the father’s and mother’s perspective — I found it beautiful and revealing.

Cindy McCain, traveling in Bangladesh, had promised a Catholic friend she would visit Mother Teresa’s orphanage there. After her tour, two nuns whom Cindy laughingly describes as “sweet and tenacious” brought two children to her. They explained that both babies would die (one suffered from malnutrition issues, the other from severe cleft palate) unless brought to the United States. Cindy said Yes to their pleas on behalf of the children. She then engaged in a battle with local officials to allow her to take the babies out of the orphanage.

As a woman operating in Bangladesh’s culture, she was at a disadvantage, and so had to take on a tough role — one the town elders had not yet experienced. Cindy won. She brought the babies back home, presenting one to her husband: “John, here’s your new baby.”

In a way that defies his tough, military persona, he describes the “extreme privilege” of receiving his new daughter — surprise or not. They found a home for the other baby with their own close friends.

The McCains’ immediate and generous Yes to taking responsibility for two children in an incredibly inconvenient circumstance is revealing — and inspiring. It is much like the response of Alaska Gov. Sarah Palin, who recently gave birth to her fifth child — a child born premature with Down syndrome.

Palin and her husband also embraced the surprise: “We knew through early testing he would face special challenges, and we feel privileged that God would entrust us with this gift and allow us unspeakable joy as he entered our lives.”

Pope Benedict’s words at the first Mass of his pontificate (which President Bush repeated during his visit at the White House) put the value of the “surprise” child in context: “Each of us is the result of a thought of God. Each of us is willed, each of us is loved, each of us is necessary.”

No matter who you are, how smart or slow you are, how beautiful or plain you look, how much or little money you have, how healthy and physically fit you are — you are necessary.

Your right to life is equal to that of all others. Even when it’s not obvious. Even when your existence requires another’s sacrifice.

The McCains agree. The Obamas disagree. That is why the choice between the two agendas is easy.

Marjorie Dannenfelser is president of the pro-life Susan B. Anthony List. She writes from Arlington, Virginia.