Who do you think the two political parties would turn to as a replacement candidate should such a terrible attack take place?

Would the VP candidates become the lead candidates? or would the parties get together and choose someone altogether different?

Since it has never happened before (at least for President), all I can do is speculate.

Should Bush be assassinated, then Dick Cheney automatically becomes president. I would imagine he would stay at the top of the ticket and would have to quickly select a VP. When Spiro Agnew resigned as VP, Nixon nominated Gerald Ford for VP, who was confirmed by the Senate. When Nixon resigned, Ford became president and nominated Nelson Rockefeller (sp?) as VP, who was subsequently confirmed. Should something terrible happen to Bush, especially if it were close to the election, then I wonder if there would be time to get a VP confirmed through the Senate.

On the other side, it seems likely that the Democrats would put Edwards at the top of the ticket (assuming he wasn't killed at the same time, of course). They'd then have to quickly select a new VP candidate.

There has been at least a couple examples where a candidate for another office, such as Missouri's Mel Cardihan (sp), died before the election. In his case, his wife took his place. If I'm not mistaken, Kerry's wife is an immigrant, so that really unlikely scenario wouldn't be possible. More likely, the DNC would quickly select someone else to head the ticket or be the VP. I saw someone speculate that Hillary would get the nod, but that's just wild assed speculation.