Barack Obama has a Catholic problem. If he doesn't do better than John Kerry did in 2004 with this quintessential swing voting bloc, he won't be elected president. Obama's campaign understands this -- which is why they're considering allowing a pro-life Democrat, Sen. Bob Casey of Pennsylvania, to speak at the Denver convention. Sen. Casey's father, the late Governor of Pennsylvania Robert Casey Sr., was denied a speaking slot at the Democrats' 1992 convention for fear of offending pro-choice Democrats. But simply allowing his son to speak at the convention won't be enough to woo Catholics back.

Catholics are by no means a single-issue voting group. But for observant Catholics, those who attend Mass regularly and follow the Church's teachings, a candidate's position on abortion matters. Even among more broadly identified Catholics -- those who call themselves Catholic, regardless of whether they are observant -- 59 percent oppose abortion, according to a recent Time magazine poll. And Barack Obama's record on this issue will cause pause for many of them.

Like most Democratic politicians, Barack Obama favors abortion rights for women, with few exceptions. He has recently said that he might support some limits on very late-term abortions, those that occur in the last trimester of pregnancy. But when it comes to actual legislative limits, he's never found one yet he can vote for.

Take partial-birth abortion, a gruesome procedure in which the fetus is delivered feet-first, its skull punctured and its brain suctioned out, thereby killing the fetus and collapsing the skull for easy delivery of the full body. Although he was not in the U.S. Senate when it voted to ban partial-birth abortions, Obama has nevertheless heavily criticized the legislation and the Supreme Court ruling that upheld its constitutionality. "Some people argue that the federal ban on abortion was just an isolated effort aimed at one medical procedure -- that it's not part of a concerted effort to roll back the hard-won rights of American women. That presumption is also wrong," Obama told those attending a 2007 Planned Parenthood meeting. But Americans overwhelmingly oppose partial birth abortion -- 70 percent in a 2003 Gallup poll -- so Obama's views put him in a distinct minority.

Obama's most controversial action on the abortion issue occurred when he was an Illinois state senator. Bills that would have required medical personnel to treat infants who survived abortion procedures came up several times during Obama's tenure in the Illinois state senate -- and each time, Obama opposed passage. He has since tried to defend his stand by claiming that the purpose of the Illinois bills was to overturn Roe v. Wade. And he's even argued that the Illinois legislation was unnecessary because "there was already a law in place in Illinois that said that you always have to supply life-saving treatment to any infant under any circumstances," as he told Relevant magazine last month.

In fact, the Illinois legislation was introduced after a Chicago nurse, Jill Stanek, came forward to describe her own experiences "where babies were being aborted alive and shelved to die in the soiled utility room" at Christ Hospital in a Chicago suburb. Stanek testified that she held one of the infants for 45 minutes before it died after being denied any medical treatment. Clearly the legislation was not superfluous, as Obama suggested. Moreover, Obama explained his vote at the time by complaining, "if we're placing a burden on the doctor that says you have to keep alive even a previable child as long as possible and give them as much medical attention as -- as is necessary to try and keep that child alive, then we're probably crossing the line in terms of unconstitutionality."

Polls show Catholics pretty evenly divided between Obama and McCain at this point -- with 45 percent favoring the GOP candidate and 44 percent favoring the Democrat. But Obama will have a difficult time wooing pro-life Catholics, given his record -- and a speech by a pro-life Democrat like Sen. Casey won't be enough to tip Catholics in his favor. And, of course, the biggest obstacle to Obama's outreach will be pro-choice Democrats, many of them feminists who supported Hillary Clinton.

As on so many issues, Obama risks losing the far left of his party if he moderates his own out-of-the-mainstream positions on abortion in order to win more centrist voters. Instead, he'll probably continue to talk out of both sides of his mouth on this issue and hope Catholic voters don't notice.