Is it really true, as a recent Gallup poll has indicated, that 28 percent of Clinton backers and 19 percent of Obama backers would vote for John McCain? Basically logic indicates that probably not, and now via Mori Dinauer, we've got some evidence from Brian Schaffner:
In March of that year, the Pew Center for the People & the Press released a report titled "Bush Pays Price for Primary Victory." Following Bush's victory in the 2000 primaries and McCain's exit from the race, the Pew survey found that 51% of those who backed McCain during the primary campaign would vote for Gore in the general election. Only 44% of his supporters said that they would be casting their votes for Bush. Furthermore, a significant share of Bradley supporters also said that they would be supporting Bush in the general election, including 39% of his independent backers.
No doubt there will, in fact, be some people (Clinton supporters who are serious foreign policy hawks or some newly minted Obama supporters who've never been involved in the political process before) who'll defect for McCain if their favorite Democrat wins, but one should expect this to be a pretty small number of people.