Same as my generalized view in regards to Obama with Wright and Ayers
Is he the company he keeps? No. Does the company he keeps reflect back on him? Yes it does, in the sense that it speaks to his judgement.
Now, there's not a lot one can make from a singular instance. Additionally, every situation needs to be taken into consideration in regards to its relation to judgement. Did Santorum personally hire this person? Did a campaign manager of Santorum's hire them? I'd say both instances may speak of somewhat poor judgement, but the first would inidcate a larger bit of poor judgement then the latter on Santorum's part.
Is this guy a friend? Is he a political advisor? Is he a spiritual advisor? Is he essentially just an employee? This all matters with regards to the level of judge of character.
IE, say there's a guy who has very homophobic views that's associated with a candidate. If his association is that he plays basketball every week with the candidate then my concerns about his judge of character based on the persons views is significantly different than if his association is that the guy is a personal advisor. In the first case, whether or not the guy is homophobic isn't really relevant to the activity he does with him and he may not even know aobut it. In the second case, it does factor in more and becomes a bigger issue.
I didn't have a huge issue with Ayers by himself. I did have issues with Reverend Wright due to Obama calling him a "mentor" in a very broad and wide ranging sense. The varoius associations coming out with Obama over time however did make me question his judge of character in picking those he wanted to associate with, be mentored by, be advised by, etc which to me is problematic for a Presidnet as judge of character is an important quality given all their appointment powers.
As a singular entity, this doesn't raise a huge alarm for me from Santorum. That said, if this kind of thing became a more wide spread occurence with regards to high level campaign officials or those close to him, it'd begin to become a problem with me. However, much like I thought very little in terms of reflections on Obama with the local campaign manager hanging a Che flag up in an office, I don't view these various localized entities as much as those closely tied to the candidates staff. They typically are relatively disconnected from the candidate themselves and in place usually through multiple connections rather than direct from the candidate. If it came out differently, that'd possibly change my mind, but not seeing anything suggesting that yet.