Please, allow me to make these even easier to understand.
Why would Sen Santorum be better positioned to run for the oval office if he had not supported his president ((who backed Spector)) and elected instead to endorse Toomey?
Secondly, not everything is about party politics. There are issues BIG enough to transcend them. Getting pro-life, conservative pro-family legislators is one of them.
And it is NOT good political sense for the party and the president to support a Liberal politician who frequently stabs them in the back, and votes with the other party more than 50% of the time.
Santorum is someone who almost always votes with the party and does their bidding. That one time he could have gone against them.
Interesting that Spector's betrayal's never seem to hurt his support from Republicans at election time. It is doubtful that had Rick stayed out of it he would have lost the support of the president now.