President Obama faces a moment of judgment. He probably doesn't realize it. Up until this point, he has been innocent of the evil of abortion taking place in this nation.
As President there is nothing he can do about it (not that he seems particularly interested in doing anything).
But, when he appoints a Supreme Court justice, now he is liable. If that judge votes in favor of abortion the next time it comes up (and it is always being pressed to test the mood of the Court), then Obama takes on some of the guilt. He knows (or at least, should know) where his candidate stands. If it is not a priority, then that is judgment too.
It is important to know that judgment rarely comes about in a timely fashion. God is working things out in His time, and His greatest priority is not our time lines. Everything is worked out in eternity future.
I haven't seen any documentation of Kagan's stand on abortion. As an academic and litigator, it has little opportunity to show. This CNN article (and other places) describes her as "trailblazing", which is not really encouraging.