Does anyone really think John McCain is in this for two terms? I didn't think so.
Given that, I think an argument could be made that although Palin is filling the second slot on the 2008 GOP Presidential ticket, symbolically, she is really in the top slot.
I think there will be a noticeable, but small percentage of voters who will now vote for the ticket solely because of Palin's presence. However there is likely a substantial number of voters who were going to vote for McCain anyway who now do so with significant enthusiasm. Nonetheless, the small percentage of voters could likely put the ticket over the top.
Then she wins two successive terms literally at the top of the GOP ticket (2012 and 2016). That's three terms she's led the ticket.
I suppose you could argue that Reagan was elected to three terms, with George H.W. Bush serving as the Reagan "third term." However, Reagan's name did not actually appear on the ballot in 1988, so I don't think it's as strong of an argument.
Palin will serve as the new generation's "Reagan." I can already predict the following monikers:
"Palinomics""Palinesque""Q: What won't Sarah wear her New Jersey? A: Idaho but Alaska."Sarah Palin: John McCain's "Deadliest Catch."
More to come....