The upside to having Governor Sarah Palin on the McCain ticket:
1) Her youth is a good contrast to McCain's age.
2) Her conservatism offsets McCain's lack of solid conservative credentials.
3) Her polished good looks are an image enhancer for the ticket.
4) As a female she certainly will snare at least a portion of disenchanted Hillary Clinton supporters.
The downside to having Governor Sarah Palin on the ticket:
1) She hails from a state with few electoral votes.
2) She has little experience in national politics.
3) Her conservative views on issues such as abortion and gun rights could turn off some voters, particularly women.
In either case, studies and polls have indicated that vice-presidential candidates are only a minor factor in a voter's decision to vote for a particular presidential candidate.