You seem to have forgotten; she wasn’t running for President; she was running for Vice President.
Dewey vs. FDR-Truman —> Dewey vs. Truman
Stevenson vs. Eisenhower —> Stevenson vs. Eisenhower
Carter-Mondale vs. Reagan —> Mondale vs. Reagan
These were all rematches, and considered so by the voters and historians.
And they all ended the same way: the two-time losers lost even bigger the second time around.
McCain-Palin vs. 0bama —> Palin vs. 0bama would be no different.
It doesn’t matter who was on the top of the bottom of the ticket.
What matters is they were on a ticket that already lost to their opponent.