I don't know how many other candidates have had to handle this question, but that's not the point. Santorum flunked out with those statements, because he didn't say that the eligibility question remains unanswered, as he should have.
Instead of leaving it in neutral, he went to bat for Obama by declaring, "My understanding is that issue was solved." That's unconscionable and infuriating.
You mentioned Sarah Palin's take on the eligibility issue. I recall that when Trump was 'investigating' Zero's bc, she said something along the lines of, "I think it's a fair question, and ought to be looked into." (my paraphrase)
If the damn topic is so radioactive that politicians are going to burst into flame by just touching it, then Sarah's was the correct response. She took no stance, but left the question open, as a legitimate issue of concern.
Actually, windflier, Gov. Palin said BOTH ... “it’s distracting, it’s annoying” (February 2011) and that it was a legitimate question (April, 2011), after Trump made it a major issue. So you might say Gov. Palin was against it before she was for it? Both versions are easily googled and on youtube.
But, again, while Santorum didn’t give the ‘correct’ response as you and I might like, I would ask what other pol or public figure is willing to take it on? Other than Trump, I’ve see no one.