Sarah Palin was probably first considered as a vice presidential candidate as a brilliant strategic countermove if Mr. Obama had chosen Hillary Clinton as his running mate for vice president.
Mrs. Clinton would have united the Democratic party but would have galvanized the Republicans. In debates and campaign speeches, Mrs. Palin would have appeared more youthful and optimistic in contrast to the seriousness of Mrs. Clinton.
I believe it will come out sometime that the choice of Sarah Palin as vice presidential candidate was considered before either party's convention.