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DMZ’s question seriously misconstrued what meadsjn posted, so that answer you wait for could be a long time coming. - It transfered motivation from McSwine to Palin.
McCains numbers were dropping like a rock in late 2009, so he asked Palin to help him out, in return for him becoming more conservative so he wouldnt be such an embarassment to Republicans everywhere.
As written, it is clear that McCain requested something of Palin (her being his veep), with her specifying the condition that he become more conservative. I know of no other way to read 'in return for'.