I'm guessing no matter what tactics one applies to Obama's choice, that he has ensured a fallback so that even if his scapegoat nominee were to be confirmed, that the nominee would be fairly inline with Obama's most important issues, gun control being near the top of that list.
Given the current makeup of the SC, even a "moderate" on gun control would be severely detrimental to gun rights. Though I'm not sure that even if the nomination was made by a Republican winner in this election, that we would get anyone who is a strong constitutionalist. Take your pick of Trump or Cruz, I don't think either one could get anyone more conservative than a Roberts through the Senate.