What on earth makes you think it would "get ALL the GOP vote"? This is the party who's primary voters just chose McCain in 08' and Romney in 12'. The first problem with your premise is that a majority of Republican voters aren't even very conservative to begin with. Sure, the activists and grass roots are, but that's not even the bulk of the voters in the party. What on earth makes you think that Dem women would vote for Palin/Bachman? Where is the evidence for this? Democrat women vote largely on emotional appeals and the desire for free stuff - not out of solidarity with the sisterhood. On top of that, Palin really doesn't poll well with women outside of conservative circles. Further, Bachman flopped in her national run last time around - why would we think she'd have a better connection with voters this time around. If the ticket were Palin/Bachman we'd probably lose so bad it would wipe us out on downticket races throughout much of the country.
The worst they will do is stay home- but Conservatives already did that for McLame and Romney.
So, I don't think it is a negative on the GOP side. If anything it will be a huge plus on GOP Conservatives- McLame would have lost in a huge landslide if he did not add her to the ticket.
Plus, once she speaks, she will energize people even more, like Reagan did.
Then, on the D side, there are some D women who will say “Oh- an all-women ticket? I'm voting for that” (remember we are talking about people stupid enough to be democrats. And they turned out to vote for “the first black man”